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THIS book comprises six talks broadcast in the 
National programme in the Spring of 1933. 
Conversational English differs markedly from the 
written language, and it is essential to a good 
broadcast that the language should be conversa- 
tional. Indeed, it is almost a criterion of a good 
broadcast that it should look queer when printed. 
We have therefore made slight alterations, but 
we have not rewritten the whole in the ordinary 
language of print. Certain parts of the book, such 
as the end of Chapter IV, were not actually 
broadcast. We wish to express our gratitude to 
the British Broadcasting Corporation for kindly 

permitting publication in book form. 

J. R. B. 
J. B. S. H. 




By John R. Baker 







By J. B. S. Haldane 



University Demonstrator in Zoology -, Oxford 


A Biologist's View of Everyday Life 

How much does each of us know about how the 
world appears toother people? I confess I have not 
the slightest idea how it appears to a Chinaman, 
but I am not referring to people of other races. 
I mean people of my own race who do different 
things from me. It is often said that we have no 
idea even how colours appear to anybody except 
ourselves. Just think of the tremendous amount 
we do not know about how all sorts of things 
appear to other people, unless we happen to be 
extraordinarily imaginative. 

About sixteen years ago, when I was a boy 
of sixteen, I was very keen on the microscopical 
animals and plants that float about in the sea, and 
I had an idea that I could invent a better net for 
catching them than anybody else had invented. 
To make this sort of thing you want very fine 
silk netting. Now millers want very fine silk 
netting, to use in sieves. They call it boulting 
cloth. So I wrote to a large firm that makes 
machinery for milling, and got a square yard of it. 
That is the only object I have ever bought from 
Mr. C., but every year since then Mr. C. has 


Biology in Everyday Life 

sent me a calendar; and every year since I have 
had a study, it has hung in my study and told me 
the date. It is not an ordinary calendar at all. On 
each of its twelve pages are pictures of milling 
machinery. Every April, amid a maze of com- 
plicated machines, I search out and find a little 
gadget called what do you think? a pritchel. 
Sixteen years have gone by. I have grown from a 
boy to a middle-aged man, and still to this day 
I do not know what a pritchel is for. It looks 
uncommonly like a flat-pointed pencil in the 
picture. If a pritchel is a problem, what of the 
other objects that Mr. C. shows to me each year? 
What of this? "One harp or quarter of millstone 
with ten qrs. running with the sun." I am out of 
my depth here. The picture looks like a plan of 
fortifications round a camp. And then a "round 
bottom tin scoop"? How can one guess its 
function? Or a "band sack hoist"? Or even a 
"continuous worm"? 

Here is a field of knowledge of which I know 
nothing, absolutely nothing whatever. You have 
your field of knowledge, on which you are an 
expert. I calculate that the chances against your 
field being biology are about fifty thousand to one, 
so your outlook is almost certainly different from 
mine. The point of this first chapter is just to 
show you what it feels like to be a biologist. 

A Biologists View of Everyday Life 

Perhaps you will ask why I have let these 
sixteen years go by and never found out what a 
pritchel is. That is a perfectly good question and 
I have a perfectly good answer to it. I have a 
young friend. When I first met him I asked him 
what he was interested in. His answer surprised 
me. "Everything", he said; and so he is. I expect 
he knows what a pritchel is. But if we try to 
know about everything, then we can only have a 
superficial knowledge of everything, and no deep 
knowledge of anything. Some degree of specializa- 
tion is absolutely necessary if we are going to find 
out something new in any department of know- 
ledge, and my object in life is to find out unknown 
things about living organisms. Of course, it is 
wrong to specialize too much. I know a man who 
specializes on cockroaches, and not only on cock- 
roaches, but on the cockroaches of a particular 
group of islands! A friend of mine says that a 
specialist is a man who wants to know more and 
more about less and less. We shall not make any 
world-shattering discoveries in that way. As in 
most things in this life, the even mean between 
the extremes is what we should aim at. 

We are all of us rather apt to think that other 
people's lives and outlooks are rather like our 
own, until we begin to think seriously about it, 
and then suddenly we find that we know nothing 


Biology in Everyday Life 

about other people's. Charles Darwin, the greatest 
biologist of all time, spent many years of his life 
studying barnacles. He had a room in his house 
where, day after day, he studied his barnacles. 
That probably seems extraordinary to you. But 
did it seem extraordinary to his family? Let me 
tell you. His family were one day shown round a 
friend's house. We will call the friend Mr. A. 
The hall, the dining-room, the drawing-room, and 
no doubt the various domestic offices were re- 
viewed in turn. One of Darwin's little boys was 
there. The house would have seemed a very 
ordinary house to an ordinary boy, but to Darwin's 
boy it seemed an extraordinary house. When they 
at last left to go home, he could contain himself 
no longer. "But mother", he asked, "where does 
Mr. A. do his barnacles ?" Darwin's son had 
accepted the "doing" of barnacles as a natural 
part of every grown man's existence. 

I am not going to say what it is like to work at 
barnacles, or even to work in a laboratory at all, 
but I want to give you some idea of what it feels 
like to be a biologist. Probably you think biologists 
are very funny even extraordinary people ; and 
probably you think that they are concerned with 
things that don't matter a bit. Often things which 
do not matter at all at the time they are discovered 
become extraordinarily important a generation or 

A Biologist's View of Everyday Life 

so later. What about the man who was studying 
the reproductive organs of grasshoppers and dis- 
covered the secret of sex determination ? One day 
fairly soon the world may be topsy-turvy as a 
result of that discovery. Our newspapers are full 
of politics, politics, politics. It cannot be very long 
now before ordinary politicians take their proper 
places in the background, and biologists begin 
to control human life. Already this great revolu- 
tion is beginning. I am reserving all that for 
later chapters. In this first chapter I am asking you 
to allow me to introduce myself and show you how 
the biologist is alive to everything that is going 
on around him, and alive in a special way. 

Well, then, the biologist awakes in the 

I am awakened by the pulling of blinds. I 
am dimly conscious of my housemaid's movements 
about the room. She has got up before me and 
now she is doing things for me. Why? Is there 
anything like that in the animal kingdom ? 

Certainly there is. There is even the exact 
counterpart of complete slavery. There is an ant 
called Polyergus rufescens^ which is common in 
parts of Switzerland. 1 The workers are very 
ferocious and never look after their own young, 
as the workers do in all ordinary kinds of ants. 

See Wheeler. 

B 17 

Biology in Everyday Life 

What is more, they are not even capable of 
collecting their own food. How do they manage 
to exist, if they cannot look after themselves? 
They enslave other kinds of ants, especially one 
called Formica fusca. Usually there are about six 
times as many Formica as Polyergus in the nest. 
Each Polyergus has half a dozen slaves to look 
after it. 

The slaves are workers, which do not breed, 
In time they die off, and if they were not replaced, 
the poor Polyergus would be as helpless as I 
should be if my cook and housemaid and nurse 
were suddenly to desert me. But there is just one 
thing that Polyergus can do, and that is to get 
more slaves from time to time. In the summer 
small parties of Polyergus go off and look at the 
Formica nests in the neighbourhood. Then one 
afternoon in July or August all the Polyergus 
ants in the nest march out together in a dense 
column. They go straight to one of the Formica 
nests. It is exactly like an Abyssinian slave raid. 
It looks as though they had investigated all the 
nests round about and for some reason chosen 
this special one for attack. If the nest is defended, 
they kill the defenders with their huge jaws. They 
carry the pupae back to their own nest. In due 
course the pupae change to adult ants, which 
accept the Polyergus nest as their natural home, 

A Biologist's View of Everyday Life 

and spend their days slaving for their masters. 
The architecture of the nest is exactly that of 
the slave ants. Their masters cannot even excavate 
a nest. 

We have not got far with the day yet. I have 
just woken up. From my bed I can see the basket 
in which my dog. Merry, sleeps. I keep him just 
as a pet, and because I like him. He is of no use 
whatever. He is a cocker spaniel, but I do not 
shoot. If a burglar were to come, he would be 
almost certain to go up to him and lick him. I 
keep him simply as a pet. I like patting him and 
talking to him and taking him for walks. Do any 
other kinds of animals keep pets ? 

There is a minute beetle called Hetaerius that 
lives in ants' nests in Europe and North America. 
Hetaerius does nothing whatever to help in the 
economy of the ants' nest. Yet the ants feed him: 
in fact, he relies entirely on being fed by the 
ants. Why do the ants tolerate him? Simply 
because they like petting him. The ants lick him 
all over the face, and appear to enjoy doing so. 
When they start trying to lick his face, he pulls 
his head back under his thorax, and the ant cannot 
get at him properly. So the ant throws up some 
of the contents of its stomach, which the beetle 
likes to eat. Directly the beetle puts his head 
forward to eat, the ant starts licking its face 

Biology in Everyday Life 

effusively. After a bit the beetle often pulls his 
head back again, and the ant has to produce some 
more food to induce it to allow itself to be fondled 
again. The ants like carrying the beetles about 
and also roll them over and over like barrels. 
So it is not only human beings that like pets. 

One of the first things I do is to put on my 
spectacles, as I am shortsighted. That is to say, 
the lenses of my eyes are of the wrong shape. It is 
rather annoying to remember that they produce a 
perfectly good image of everything, but in the 
wrong place. Instead of producing the image on 
the backs of my eyeballs, where the sensory cells 
are that would convey the image to my brain, 
they produce it in front of them, where there are 
no sensory cells. If I put concave spectacles in 
front of my eyes, the image is thrown back on to 
the right place and I see clearly. 

The frames of my spectacles are partly of what 
is called tortoiseshell, but tortoiseshell is not 
actually the shell of the tortoise. It comes from 
the hawksbill turtle. Turtles, of course, have 
paddles. Tortoises have separate fingers and toes. 
The turtle that produces tortoiseshell is not the 
same as the turtle which finds its way into soup. 
The tortoiseshell turtle eats fish. Like most 
carnivorous animals, it is not very good to eat. 
The turtle which we eat eats seaweeds. 


A Biologist's View of Everyday Life 

I must get up and have a wash. Here is my 
sponge. I propose to wash with the skeleton of a 
marine animal. There is not any doubt the sponge 
is an animal. Plants are living organisms which 
can live on inorganic salts, or are obviously 
related to ones which can. Animals are living 
organisms which require organic matter ready 
made for them. They either eat plants, or else 
they eat animals that eat plants, or eat animals 
that eat animals that eat plants, or at any rate 
somehow or other get organic matter that was 
made from inorganic salts by plants in the first 
place. A sponge feeds on microscopic plants and 
animals which float about in sea water. It is 
really a sieve through which the water is passed 
by the lashing of microscopic whips. The thing 
we wash with is just the skeleton of it. There 
are hundreds and hundreds of different kinds of 
sponges, but only a few of them are any good for 
washing. Most of them have masses of hard 
pointed spicules in them, and they would be most 
uncomfortable things to put against one's skin. 

Then what a remarkable process shaving is! 
To the biologist it presents all sorts of problems. 
Why do hairs grow on my face ? One knows this 
much. There exist certain glandular cells in the 
reproductive organs of men, which make a 
chemical substance and push it out into the 


Biology in Everyday Life 

blood. It circulates in every part of the body, 
and makes the different parts grow in the male 
way. The substance is what is called a hormone, 
or chemical messenger. That is a partial explana- 
tion, but it does not explain the use of a moustache 
and beard. We call organs of this sort secondary 
sexual characters. By that we mean that they are 
not essential sexual characters in any obvious way. 
The wattles of cocks are an example. They are 
supposed to be an attraction to the female, and 
Darwin thought that in the course of evolution 
they gradually got bigger and bigger because the 
hens tended to choose for mates the males with 
the biggest wattles. But beards! Most men seem 
to get chosen all right without them. They are a 
bit of a mystery to the biologist. Perhaps they 
were an attraction to the female of our pre-human 
ancestor, and we have simply retained them, 
while women have changed their opinion as a 
result of education. If a modern English girl were 
cast up as a baby on a desert island and managed 
to survive, what would she think if she were 
brought to England ? Would she fall for the first 
bearded man she saw? I wonder. 

Many men think the hair on their faces grows 
more quickly if they shave than if they do not. 
Recently a woman in America got four men to 
send their shavings to her over a period of nine 


A Biologist's View of Everyday Life 

months, and she made elaborate measurements of 
them. Sometimes they shaved every twelve hours, 
sometimes they went four days without shaving. 
It made no difference whatever. The hair went on 
growing at the same speed whatever they did. 

When I want to shave, I have got to have a 
foam of bubbles to support the hairs while they 
are being cut, and a slippery fluid to let the razor 
slide along easily. Soap does the trick. It is an 
extraordinary fact that for making this slippery 
foam there is nothing so good as the hair of the 

Have you ever seen a badger? One does not 
often see one, because they are nocturnal. They 
live in holes. Some people think it fun to pull 
them out of their holes with specially made tongs 
and then kill them. One must have an extra- 
ordinary idea of the meaning of words if one calls 
that sport. Badgers are most interesting animals 
in several ways. Their long hair seems to be a 
protection against attack as well as against cold. 
Wherever one catches hold of a badger, he seems 
able to bite. That is partly because his hair is so 
long, and partly because his skin is so extra- 
ordinarily loose. He can turn inside his skin, so 
to speak. It seems rather extraordinary that a 
structure that has evolved for the purpose of 
protecting the badger and keeping him warm 


Biology in Everyday Life 

should be found to be the best possible instrument 
for making a lather with soap. 

People often think badgers are closely allied to 
bears, but that is not so. They come in a group 
with the stoats, weasels, otters and skunks. They 
all agree in having very few molar teeth, that is, 
teeth behind the ones that replace the milk teeth. 
Bears have two above on each side, and three 
below. The stoats and badgers never have more 
than one molar tooth on each side in the upper 
jaw, and only one or two below. We have three, 
of course, both above and below, the last being 
the so-called wisdom-tooth. Lots of animals have 
three, but it is rather unusual for animals to have 
only one, both above and below, like many of the 
badger's relations. 

Well, we have got on to teeth, and now that 
I have shaved I must wash them. Is it not extra- 
ordinary that we have to wash our teeth to keep 
them in good condition? We seem to have the 
worst teeth in the animal kingdom, and fossils of 
our prehuman ancestors show that they too 
suffered from dental decay. I wonder why it is. 
One has the impression that our teeth are often 
too crowded in our mouths. If only they were 
better spaced, like most animals', food would not 
get stuck between them, and then probably they 
would not decay so fast. Why should our teeth 


A Biologist's View of Everyday Life 

be so crowded? I wonder if it can be that they 
did not get proportionally smaller while our jaws 
were decreasing in size. There is no doubt that 
our ancestors had much bigger jaws than we. 
They stuck forward something like a gorilla's or 
chimpanzee's. Nearly all the fossil skulls of our 
remote ancestors show that. (Actually I should say 
the relations of our remote ancestors, because of 
course there is no evidence that any of the fossil 
skulls really represent actual ancestors of modern 
man.) The aborigines of Australia still retain 
the large jaw, but it is not nearly so prominent as 
those of the fossil skulls, and theirs are not so 
prominent as the gorilla's. 

Let us get dressed. Do any animals dress? 
That all depends on what one calls dressing. By 
dressing, I mean putting a bit of the environment 
on oneself for protection. Certainly there are 
animals that do that. The caddis-worm is an 
obvious example. You have probably seen him. 
He lives at the bottom of ponds. He is the 
larva of the caddis-fly, but you do not often see 
caddis-flies. That is because caddis-flies are dull- 
coloured and do not often fly about. They prefer 
to remain hidden. The larva or caddis-worm 
takes tiny bits of vegetable matter or grains of sand 
and makes a little tube out of them in which he 


Biology in Everyday Life 

My clothes are sewn together. The caddis-worm 
does not exactly sew, but there is a tropical ant 
called Oecophylla which practically sews. I really 
think that Oecophylla is one of the most wonderful 
animals in the whole of nature. It does not sew 
to make clothes, but to make its nest. It makes its 
nest of leaves sewn together at the edges with 
silk. Now no adult insect 1 makes silk, though 
insect larvae that is caterpillars often do. The 
larvae of Oecophylla make silk. They make it in 
two glands in the abdomen and it oozes along a 
tube in a sticky condition and finds its way out 
by a pore on the lower lip. Ant larvae are abso- 
lutely unable to move about and could not possibly 
sew with this silk. What is the use of it ? What I 
am going to tell you is practically unbelievable, 
but it is true nevertheless. To make a nest, a row 
of ants holds the edges of two leaves together. 
Then other ants line up on the other side of the 
leaves at their junction. They actually sew them 
together, holding the leaves in their jaws and 
passing the larvae to and fro across the gap. They 
use the larvae as living reels of silk. The silk sticks 
to the leaves where it touches them. 

Now brushing the hair. My hair is quite short. 
That is because I get it cut every now and then. 
Does any animal besides man have the habit of 

1 Except the fly Hilara. 

A Biologist's View of Everyday Life 

cutting bits off itself? The Motmot is a bird 
something like a kingfisher. He lives in Central 
America. He has an extraordinary habit. 1 He 
nibbles off the barbs of his middle pair of tail 
feathers all the way along except just at the tip, 
where he leaves a racket-shaped end. All along 
the rest of the feather he leaves nothing but the 
bare quill. I say "he", but actually both sexes do it. 

I do not only brush my hair; I also comb it. 
Animals, too, sometimes have combs. The middle 
toe of the nightjar is like a comb, and he is 
thought to arrange his feathers with it. Gannets 
and herons have a similar arrangement. Then 
there is a curious Malayan mammal called 
Galeopithecus. He seems to be allied to the 
insectivores, the mole and shrew and their allies, 
but he is bigger than these, and he has got a 
membrane stretched on each side between his 
arms and his legs, so that he can glide about from 
tree to tree. Galeopithecus has a comb. His lower 
front teeth are comb-like. They are really very 
extraordinary to look at. Perhaps you could see 
them in a museum, if you happen to live in a 
big town. 

Combs are sometimes made of tortoiseshell, and 
sometimes they are synthetic, but often they are 
made of whalebone. What is whalebone ? First of 

1 O. Salvin, Proceedings of Zoological Society of London, 1873 (p. 429). 


Biology in Everyday Life 

all whalebone is not bone. It is a horny substance. 
It is produced by the toothless whales only. It 
hangs from the roof of the mouth in ridges. The 
lower edges of the ridges are frayed. The whale 
fills his mouth with water, and then raises his 
tongue. In big specimens his tongue may weigh a 
ton. When he raises it, the water is squeezed out 
between the frayed ends of the whalebone. The 
minute floating animals in the water are held back 
by the whalebone, which is really a sort of filter. 
He licks them off and swallows them. It seems 
extraordinary that such a huge animal should feed 
on almost microscopic food, and perhaps even 
more extraordinary that the substance which has 
evolved to act as a filter for the whale's food 
should have been found to be one of the best 
substances for preventing human hair from getting 

If I were to go right through my day, it would 
take many chapters, but we have more serious 
business to which to attend. This is really just an 
introductory chapter, to give an idea of a biologist's 
outlook on things in general. In the next chapter 
we shall discuss social animals. Man is essentially 
a social animal. We must study social animals in 
some detail first, so that even the second chapter 
will be to some extent introductory. 



Social Life in Animals 

WHAT is the greatest feat of heroism that you 
have ever heard of? I suppose that heroism usually 
consists in disobeying a strong instinct for some 
worth-while object. Usually it is the self-preser- 
vation instinct, I suppose, to which the hero is 
superior. What do you yourself regard as the 
greatest act of heroism ? I know what I think, and 
the ordinary self-preservation instinct was not 
concerned. My hero rose superior to the herd 
instinct. Mr. Courtauld went into the interior of 
Greenland with a party, and then remained there 
when the party returned to the coast. He remained 
there throughout the black Arctic winter abso- 
lutely by himself, with not a single human being 
within 1 20 miles. He completely disobeyed one 
of the strongest instincts we have, for the sake 
of making observations on the weather in a place 
where practically nothing was known before. 1 

Have you ever been alone? How far is the 
farthest you have ever been from any other human 
being? And how long did you remain at this 
distance ? 

1 The Polar Record, No. 4, July 1932. 


Biology in Everyday Life 

We are so obviously social animals that we do 
not often bother to think about it, or to ask our- 
selves whether many animals are like ourselves 
in that respect, or whether perhaps it is rather an 
unusual phenomenon in the animal kingdom. 

Let us look at the minutest animals of all first, 
the little very simple beasts that swim about in 
ponds and which we have to use a microscope to 
see at all. Most of them are not social : I mean they 
do not depend on others of the same sort as them- 
selves. They multiply by dividing into two. Each 
soon grows the missing part. They are so simple 
that that is not difficult. In the higher animals 
that would be obviously impossible, because 
neither half could get on for a moment without 
the other. Even if each had the power of growing 
the missing bit, it would not be able to, because 
it would be dead from loss of blood before it had 
time. Each of these little beasts is only a speck 
of living matter, with nothing like blood and no 
complicated organs, so things are easy for it. 
After dividing, the two new individuals separate 
and swim away and go about their own businesses 
and pay no attention to one another. There was 
one individual, and now there are two : that is all. 

Now some species do not behave like that. 
When one divides into two, the two do not 
separate, but stick together. Each of them 


Social Life in Animals 

divides, so now there are 4, and when they 
divide again there are 8, and they still stick 
together and go on dividing. Soon we have 16, 
and then 32 and 64 and 128 and 256 and 512 
and 1,024 and 2,048. We are into thousands at 
the tenth division. The little beasts are growing 
all the time. Well, you will say, we shall be able to 
see it soon. Why have we not all seen one of these 
creatures? Wait a moment. Perhaps you have. 
Fifty divisions give us countless millions of little 
beasts, and even if they are very small, the total 
size must be quite great. Do all the little beasts 
look exactly the same ? They do not. The ones on 
the outside become flattened and horny. The ones 
right in the middle form themselves into a tube, 
and they are the ones that are the best at eating. 
They do enough eating for all the other ones put 
together. They are protected from harm by the 
horny ones on the outside, and in exchange they 
give up some of their food to the horny ones. 
The two sorts help one another. Another sort 
makes a hard substance which gives the whole 
collection of them a certain amount of strength ; 
and others are especially good at contracting, 
and they enable the whole collection to move 
about and get food and escape from enemies. 
What a wonderful collection of little beasts, all 
being so self-sacrificing! Not one is working 


Biology in Everyday Life 

just for itself. They all work for the common 

Are these wonderful collections of little beasts 
very rare ? If we hunt for them, shall we be able 
to find one and study it ? Where shall we look ? 

Do not bother to look. You are one yourself. 
That is all you are nothing else. If you did not 
mind me hacking you about, I could take a little 
bit of any part of you and show it you under the 
microscope, and you would see the tiny beasts 
which compose you. 

So you see, in a sense you are not an individual, 
but a mass of millions of individuals and nothing 
else. We may call you an individual of the second 
grade, made up of millions of individuals of the 
first grade. Nearly always all the tiny individuals 
work together for the common good of the second 
grade individual, but just sometimes some of them 
in one part begin multiplying indefinitely, and 
will not stop, and these ones do nothing for the 
common good. On the contrary, they poison it. 
Then we have cancer. Luckily the rays given off 
by radium check their multiplication. 

We have studied two grades of individuality. 
Are there any more grades ? 

Take the sea anemone. It is an animal that 
lives in rock pools round our coasts. There is a 
circle of tentacles round the mouth and often they 


Social Life in Animals 

are of bright colours. These are individuals of the 
second grade like you and me, but in the tropics 
there are anemones that divide into two, and the 
two into four and so on, until there are hundreds 
or thousands. They do not separate from one 
another. They remain attached like super-Siamese- 
twins. Their insides are connected, too, and so one 
cannot starve while another has food. They all 
together make a single solid rock-like skeleton. 
We call the whole mass a coral. It may be yards 
across. It is an individual of the third grade. 

We can extend that term a bit. Supposing the 
anemones separated from one another, but still 
remained in a group and helped one another in 
some way. Should we be able to talk about the 
third grade still ? I do not see why not, so long as 
the whole group worked together for the common 
good. This sort of third grade individual is not 
rare in the animal kingdom. A hive of bees is an 
example. An ants* nest is an even better example, 
perhaps, because ants have carried the thing 
farther than bees. In a hive of bees you find males, 
females and workers, but in an ants' nest you may 
find males, females and more than one sort of 
worker. When I say more than one sort, I do not 
mean simply that some of them specialize at one 
thing and some at another. It is not just that. 
Their bodies are specially constructed for the 

c 33 

Biology in Everyday Life 

particular work they have to do. Among many 
kinds of ants there are ordinary workers and also 
soldiers. The ordinary workers do the ordinary 
work of the nest, such as carrying pupae about 
and getting food. They are ordinary looking ants. 
The soldiers are most extraordinary looking ants. 
They are much bigger than the ordinary workers, 
with a head that is disproportionately enormous, 
with huge savage jaws in front. The soldiers' 
job is to guard the nest from attack. 

That is interesting; but here is something ever 
so much more so. In the honey ants the ordinary 
workers do all the ordinary work of the nest, 
and also collect a sugary fluid that exudes from 
oak galls, and another sweet fluid called honey 
dew, which is produced by plant lice. The ants 
stroke the plant lice with their feelers till they 
exude it from the hind end of their body. The 
workers then eat it. Many sorts of ants do that, 
but the honey ants now behave in a most extra- 
ordinary way. They go home, and enter special 
chambers in the nest, where an extraordinary 
spectacle presents itself. These special chambers 
have smooth floors and walls, but the ceilings are 
rough, and to the ceilings a large number of ants 
are attached. Ants, I say, but you certainly would 
not call them ants unless you knew, because they 
look much more like little footballs. Their abdo- 


Social Life in Animals 

mens are tremendously swollen, and the thorax 
and head look like little after-thoughts attached at 
one side. Those repulsive abdomens are stuffed 
full of the sweet fluid that the ordinary workers 
bring back. When they come back, they approach 
the living jam-jars and vomit, and the living jam- 
jars eat the vomit and grow even fatter still. They 
can move a little about the ceiling, but if they 
lose hold and fall to the floor, they are so fat that 
they cannot get up to the ceiling again. There they 
stay, some hundreds of them in a big nest. They 
may live there for years. If there is a period of 
food-shortage, all the ants of the nest come and 
cause them to vomit in their turn. That is the 
use of them to the nest as a whole: they are 
living food-stores. It is not certain whether all 
the worker ants in the nest have the capacity to 
swell and become food-stores, or whether some 
of them are from the beginning different from 
the rest. 

Among the backboned animals there are plenty 
of social kinds, but there are not any cases of 
different types within a single kind, except so far 
as the male is different from the female. There is 
nothing corresponding to a soldier ant, which is 
structurally adapted to its special job. 

Among the mammals the most obviously social 
are the marmots, beavers, vizcachas, horses, deer, 


Biology in Everyday Life 

oxen, antelopes, sheep, goats, porpoises, dogs and 
wolves, seals and sea-lions, fruit-bats, many 
monkeys and man. What advantage do they get 
from being social ? In the great majority of cases 
the advantage is simply protection from flesh- 
eating enemies. Often they have ways of warning 
one another of the approach of danger. You have 
probably heard rabbits stamping with their hind 
feet for that purpose. Among antelopes definite 
sentries are set. While the herd as a whole is 
feeding in the open, one or two individuals mount 
guard on any suitable little hillocks and keep a 

In social animals an instinct to keep with the 
herd is absolutely necessary. The way sheep 
follow one another unquestioningly is proverbial. 
We are social animals ourselves, and in crowds 
we are extraordinarily easily led to follow one 
another, to do things which we would not think 
of doing if we were by ourselves. In America 
whole crowds go off to prisons and drag out 
negroes who have not been tried for any offence 
and hang them. We see here the herd instinct at 
its worst. If you took those lynchers separately, 
you would find that nearly every one of them 
wanted the negro to have a proper trial. Yet in 
a crowd they all are raving mad to kill him. 

The herd instinct has both its bad and its good 


Social Life in Animals 

side. Altruism only occurs in social animals. 
Altruism is an action for the benefit of other 
members of the same herd, and morality is, or 
should be, based on it. Altruism satisfies our herd 
instinct, and therefore makes us happy, just as the 
satisfaction of other instincts does. Some people 
have scarcely any of this instinct, and are abso- 
lutely selfish. These people sometimes argue that 
no one ever does an unselfish act. They say that 
every apparently unselfish act is done so as to 
get some benefit in a roundabout way. That is just 
nonsense and ignorance: a certain amount of 
altruism is instinctive in normal people. 

The herd instinct makes us like to be in 
crowds. Probably television will one day enable 
us to have cinema shows broadcast to us in our 
houses, but I am sure most people will still 
flock to cinemas, for the sake of the satisfaction 
they get from being in a crowd which is swayed 
by the same emotions. 

I have said that the advantage of being social 
is usually protection against enemies, but of course 
that is not so with the dogs and wolves. With these 
carnivorous animals the advantage is that they 
can attack animals which are far too big for one 
of them to attack alone. It is rather curious that 
societies for the sake of offence are rare. Also it is 
curious that such a close relative of the dog as 


Biology in Everyday Life 

the fox should be completely non-social. The 
advantage of the dog as a pet is simply due to its 
herd instinct. It attaches itself to its master as it 
would to the pack in the wild state. 

A large herd cannot act together for the common 
good unless there is some leader to follow. Among 
wild dogs and wolves the leader is always an old 
male. The younger males want to be leaders also, 
and fight him for the leadership. He holds on as 
leader so long as he is the strongest; but when 
he gets old, he is beaten in a fight, and a younger 
male takes his place. This is probably quite an 
effective system, because a dog that is good at 
fighting will probably also be good at hunting 
the animals on which the pack feeds. 

Now let us look at a few other social animals. 
Let us look at the vizcacha first. This is a rodent 
which lives in South America. It is not absolutely 
unlike a rabbit with short ears and a bushy tail. 
It lives in villages of twenty or thirty members. 
There are about a dozen burrows in the village, 
and all the burrows intercommunicate under- 
ground. Like most social animals, vizcachas talk 
to one another a good deal. Of course, they have 
not got a proper language, with words denoting 
definite things, but they make a great variety of 
sounds. No doubt this helps to keep the herd 
together. A sudden change in the sound would 


Social Life in Animals 

indicate alarm, and all could escape into the 
burrows before most of the members of the 
village had any idea what the danger was. Like 
other social animals, the vizcacha is altruistic. If 
one of the community is carried off by a peccary 
(a sort of pig-like animal that lives in South 
America), its friends try to rescue it. 

Occasionally a new village is formed. Hudson 1 
says that the vizcacha that founds a new village is 
always a male. He goes and digs his burrow in a 
new place, away from any other village, and later 
gets a female to live there with him. As the 
family grows, a new community is gradually 
built up. 

We have seen that a male is the leader of the 
pack of wild dogs and the founder of a new village 
among the vizcachas. Is the male always the 
leader among social animals? Certainly not. 
Among red deer the herd is led by an old female. 
The old males lead a non-social life. In the 
mating season the herd breaks up. The males 
fight for the possession of the females, but there 
is no fighting for the leadership of the herd. 

The female often has duties that one might 
not expect of her. People often imagine that it is 
a sort of law of nature that the female is the weaker 
and more timid sex. That is absolutely untrue. It 

1 W. H. Hudson, The Naturalist in La Plata, Dent, 1903. 


Biology in Everyday Life 

is the female lion that teaches the young to hunt. 
In spiders the female is often the larger sex, and 
in many species it is the rule that directly after 
courtship she kills and eats the male. It is not at 
all an uncommon thing for the female to be the 
larger sex. This is especially so among the savage 
birds of prey, for instance, the kestrel and golden 
eagle. The female sparrow-hawk is much larger 
than the male. It is said that if a pair of goshawks 
is caught and put in a cage, they always fight, and 
the female always kills the male. 1 The phalarope 
is a northern wading-bird. The female is both 
larger and more brightly coloured than the male, 
and takes the more active part in courtship. It is 
the male that sits on the eggs. 

In the most diverse groups of the animal 
kingdom we come upon species in which the 
male is minute compared with the female, and 
parasitic on her. There is a marine worm in which 
the female is about the size and shape of a plum, 
while the male is about a twentieth of an inch long 
and lives inside her kidney. Then there are the 
oceanic angler fishes. If you live in London you 
can see splendid models of them in the main hall 
of the Natural History Museum at South Ken- 
sington. The male is a tiny little object which 

R. Lydekker, Wild Life of the World, Vol. I, Warne, London 
(no date). 


Social Life in Animals 

attaches itself to the skin of the female by its 
mouth and never lets go. It actually fuses with 
the flesh of the female, and is nourished by the 
foodstuffs circulating in her blood. 

Perhaps it is not beside the point to mention 
the otter. The young are not instinctively aquatic 
at all. They are forced into the water and taught 
to swim and catch fish by the female. The male 
takes no part in their education. 

Now we must get back to our social animals 
again. I only wanted to make it clear that the 
superiority of the male sex is by no means a 
law of nature, and we must not be surprised 
when we find a female leading the herd in a social 

Social animals can work together and make 
things that solitary species never could. The beaver 
is the best example. The beaver is a gnawing 
animal a rodent rather more than three feet 
long, counting his tail. His tail is flat when looked 
at from above. He has thick brown fur. He eats 
the bark of trees. He is very clumsy on land. He 
always likes to be near a stream, because he is 
extremely agile in the water, and can easily 
escape from his enemies, the bear and wolverene. 
Now, streams have a way of drying up in North 
America, where he lives. So what does he do? 
He helps to do something that he could never do 

Biology in Everyday Life 

by himself. The whole community works together 
and builds a dam across the river, to keep the 
water permanently at a high level. They cut down 
trees by gnawing through them near the base, and 
then cut off the branches and cut the trunks up 
into convenient logs. If the trees are close to the 
river, it is easy for them to transport the logs to 
the site of the dam. If there are no trees close to 
the river, they make a canal from the river to 
where the trees are, and float the logs down it. 1 
They build the dam of logs and mud, weighting 
it down with heavy stones. 

There is one special reason why they want to 
have deep water always, and that is to keep their 
front doors under water, so that no land animal 
can enter their houses. Their houses are great 
rounded domes, about eight feet high and as 
much across. They are generally on the river 
bank, sometimes partly submerged. They are 
made of branches plastered together with mud, 
and the walls are so thick that the space inside is 
quite small. The passage from the house to the 
submerged front door may be thirty feet long. 

When a beaver is alarmed, it does something 
which is not of any use to itself, but which helps 
the other members of the community. It gives the 

1 V. Bailey, United States Department of Agriculture, Bulletin 
No. 1078. 


Social Life in Animals 

water a resounding slap with its flat tail, and the 
noise warns all the others to dive for safety. Its 
instincts are designed for the preservation of the 
community of beavers as a whole. 

Let us now take an animal that is interesting 
in quite a different way. It has no remarkable 
social instincts, but it is necessarily social from its 
abundance in the places where it lives. Probably 
you have never seen a lemming, but if you live 
in the country you have no doubt seen a short- 
tailed field mouse, and the lemming is like that, 
only a good deal bigger and much fatter in 
proportion. He lives in the high plateaux, up 
above the limit of the coniferous trees, in grass- 
land with birch and willow. He eats grass chiefly, 
and the people who live down by the coast do not 
see him. But he multiplies and multiplies, and he 
gets too numerous for the amount of grass that 
there is on those mountain wastes. If only he 
would reproduce more slowly, all would be well, 
but he does not: he breeds as hard as ever when 
he is already getting too numerous. Indeed there 
is some evidence that he breeds harder than ever 
at that time. Poor fool, he does not realize what 
is in store for him. If lemmings could moralize 
like human beings, I dare say there would be 
many good old-fashioned ones who would say they 
liked to see lemmings with a good quiver-full, 


Biology in Everyday Life 

whatever that may mean. Perhaps if they could 
take photographs, a signed photograph of il Duce 
among lemmings would be awarded to the mothers 
of more than a certain number of young. Anyway, 
they act as though they had some such stimulus to 

At last there is no more grass left nothing 
whatever to eat. This timid, secretive, mountain 
animal is forced by hunger to forsake its home 
and emigrate. In countless thousands they swarm 
down the valleys, ever westward to the lowlands 
and the sea. Their emigration is useless, but they 
are driven to it by hunger. They swarm across 
rivers and through villages, and all timidity is 
lost. Though excessive breeding is the cause of 
their trouble, they breed as they go. Infectious 
disease is rife in the overcrowded swarm. Foxes^ 
hawks and owls congregate round the emigrating 
hordes and feed upon them. Onward they go, 
farther and farther from the mountain plateaux 
above, the only region where they can live per- 
manently. At last they come to the sea. Plunging 
into it, they swim out to their death. As though the 
water were not enough punishment for their folly, 
the gulls attack them. A ship may steam for a 
quarter of an hour through an army of millions of 
lemmings. They may reach an island and gain 
temporary respite, but on they go into the sea 


Social Life in Animals 

beyond. Not one returns. Every emigrating lem- 
ming dies. The offspring of those which breed on 
the way die also. The whole venture is useless. 1 
It is caused by over-population. If breeding had 
been slower, there would always have been plenty 
of food for all. 

Up in the mountains there remains a minute 
number of lemmings which have never emigrated. 
What they find to feed upon is not known. 
Presumably they must be near starvation until the 
grass has had time to grow after the great exodus. 
Next year the number of lemmings increases. Four 
years after the year of the great exodus the 
numbers are once more enormous. Rapid breeding 
continues and the emigration is re-enacted. The 
interval between one emigration and the next is 
not always exactly four years, but it approximates 
to that. 2 It is not always a huge emigration: the 
size of it varies. But three times every dozen years 
the lemming gives us a practical demonstration of 
the folly of unregulated reproduction. 

Why do not all animals have the same trouble 
as the lemming? If no house-sparrow died except 
from old age, in a quarter of a century we should 
not be able to see the ground anywhere. It would 
be completely carpeted with house-sparrows, and 

* W. Heape, Emigration , Migration and Nomadism, Heffer, 1931. 
C. Elton, Animal Ecology t Sidgwick and Jackson, 1927. 


Biology in Everyday Life 

we should not be able to take a step without 
walking on them.Yet on the average their numbers 
remain the same from year to year. It is clear that 
they are dying off in great numbers all the time, 
and that their rate of reproduction just suffices to 
balance the loss. What would happen if we started 
a Sparrow Protection Society, and made sure that 
none died from cold or from the attacks of 
enemies ? The number of sparrows would increase 
and increase until it became so great that suddenly 
the food supply would be insufficient. Suddenly 
there would be starvation on an appalling scale, 
and sparrows would stand a good chance of being 
nearly exterminated by misplaced kindness. If 
we really wanted to protect sparrows, our Pro- 
tection Society would have other functions beyond 
applying electric warmers to their sleeping places 
and exterminating their enemies. I fancy that an 
army of birds' nesters would also have to be 
engaged to remove an egg or two from every 
sparrow's nest. 

This is not just wild speculation. In the old days 
deer lived and maintained a normal population in 
North America, They were eaten by the mountain 
lion, and their natural rate of increase was suffi- 
cient to make good the loss. In one of the American 
national parks the mountain lion has been practi- 
cally exterminated by man. That must be nice for 

Social Life in Animals 

the deer, you will say. The deer multiplied till 
there were about 30,000 of them in the park. 
Every scrap of grass was eaten. The trees were 
everywhere browsed upon as high as the deer 
could reach. Then starvation. 1 

So far as man is concerned, can we draw any 
conclusions from our study of social animals? 
Firstly, we will do well to recognize the herd 
instinct. We should allow ourselves the full 
satisfaction of obeying it whenever our reason 
tells us that it prompts us to act for the benefit 
of the community as a whole. We can see, though, 
that in animals the instinct is sometimes perverted 
in an extraordinary way. Sometimes it is a harm- 
less perversion, as when a whole flock follows its 
leader to do a stupid thing. If we think, reason 
will tell us not always to follow stupid leadership. 
But sometimes, in animals, the perversions of the 
herd instinct are ugly. A wounded cow is often 
attacked by one of its own herd, and then the 
others join in, and the wretched beast is gored 
to death. We see the same hideous sight in the 
lynching of down-and-out negroes in the United 
States of America, and in the travesties of justice 
such as the Scottsboro' case. 

Can we learn any lesson from the lemming? 
We can, but shall we ? 

1 M. A. C. Hinton, Proceedings of the Linnean Society of London, 
i44th Session, 1931-2 (p. in). 



The Determination of Sex 

IT'S not much fun being a biologist! The trouble 
is that everyone else knows better. I wonder why 
poor biologists have been singled out in this way. 
Why not chemists for a change? Chemists are 
absolutely immune. No one thinks he knows better 
than a chemist. If a chemist says that rosaniline 
is made by the reaction of one molecule of aniline 
with one of orthotoluidine and one of parato- 
luidine, he is not contradicted. No one writes to 
the newspapers and says he can make rosaniline 
out of ink and sawdust. It just does not happen. 

Perhaps it is partly because chemistry is written 
in awful symbols which frighten people off the 
subject. If so, I almost wish we had as many signs 
and barbarous words in biology, because it gives 
one rather a pain to see well-meaning people writ- 
ing pure nonsense about biology in newspapers. 
They even write books on the subject that are a 
living advertisement of ignorance from beginning 
to end. Of course everyone must be ignorant of 
whole fields of knowledge, but it is a mistake to 
lay down the law on subjects of which one knows 

The Determination of Sex 

There are branches of biology that are immune. 
No one writes to the newspapers about the devel- 
opment of the chondrocranium in elasmobranchs. 
But there are large departments of biology that 
are considered fair game. Evolution is one. There 
is one subject that ignorant people have fastened 
on to more than all the others put together, and 
that is the determination of sex. 

People often say, " Everyone is entitled to his 
opinion, " and so he is so far as insoluble prob- 
lems are concerned. But I have never been able 
to see why anyone is entitled to a demonstrably 
false opinion. I once saw a perfectly unconcerned 
gentleman walking about the streets of London 
with a large biscuit-box stuck on his head in place 
of a hat. On the box was written in large letters, 
"The day of judgment is at hand/' Well, more 
power to him ! That is all I can say. He is entitled 
to that opinion. No one can deny the possibility 
that he may be right. But why is anybody entitled 
to a demonstrably false opinion as to how sex is 
determined ? 

A lot of the misunderstanding comes from 
people not taking account of the laws of chance. 
About the same number of boys are born as girls. 
Actually about 105 boys are born to 100 girls 
in most European countries. For the moment let 
us assume equality (we shall discuss the reasons 

D 49 

Biology in Everyday Life 

for the departure from absolute equality later). 
Now suppose that sex is just a matter of chance, 
like tossing a coin. What do we mean by chance? 
We simply mean that a very large number of 
independent factors are influencing the result. 

In tossing coins and catching them we have an 
example of pure chance. What does the result 
depend on? It depends on many independent 
factors. That is the point. It depends on which 
way the coin happens to be up to start with, 
whether it is level or at an angle, how hard I 
flick it round, exactly what part of it I flick, how 
far I throw it up in the air, whether there are any 
air currents in the room, how far it has fallen 
when I catch it, and whether it does or does not 
complete a turn when it reaches my hand, which 
itself depends on what part of my hand it touches 
first, and in what direction my hand is moving. 
If all those things were absolutely exactly the same 
every time, I should get the same result every 
time. But they all vary, and they vary inde- 
pendently of one another. That is what makes 
what we call chance. The more independent 
variables, the closer the approximation to pure 

The more times I toss, the closer will the 
approximation be likely to be to one head to one 
tail. If I were to toss a million times, I should get 

The Determination of Sex 

something very close to 500,000 heads to 500,000 
tails. But I may toss six times and get four heads 
to two tails. If so, what will happen if I toss six 
times again ? What are the chances ? 

This is where many people go wrong. The 
chances are that I shall get three heads and three 
tails, not that I shall "make up" for what has 
happened, so to speak, by getting four tails and 
two heads. There is no making up for past events 
in pure chance. How could there be ? Past tosses 
do not influence any of the many factors affecting 
the flight of the coin in the next toss. 

I have got four heads to two tails. Suppose I 
am determined to toss a total of a million tosses 
altogether. IVe got 999,994 tosses to come. 
Half of that is 499,997. The final figures which 
are now more likely than any others on pure 
chance are 499,999 tails and 500,001 heads. 
That is a very close approximation to equality, is 
it not ? A good deal closer than 4 to 2 ! But the 
4 to 2 at the beginning cannot influence what is 
coming later. 

Suppose we toss a coin six times and write 
down the result, and then toss it six times again 
and write down the result, and spend the whole 
day doing that and nothing else. What should 
we find ? We should find that more of our results 
were three heads and three tails than any other 

Biology in Everyday Life 

combination. Next would come four heads to 
two tails, and two tails to four heads. There 
would be fewer still of the combination five heads 
to one tail, and one head to five tails. There would 
be least of all of the combinations six heads to no 
tails, and no heads to six tails. Try it, if you do 
not believe me. You must spend hours at it if 
you decide to try. Actually one can calculate 
mathematically how many of each combination 
one may expect. 

So far we have dealt with pure chance. If you 
let the coin fall and roll on the floor till it drops, 
it is no longer pure chance. The head side is 
ever so slightly heavier, and tends to fall down- 
wards rather more often than the tail side. It 
only makes a very small difference to the result, 
because in most cases the other factors influence 
the result much more. But just occasionally the 
coin runs levelly along the floor, and then it falls 
tails up, because the head side is slightly heavier. 
So in a very large number of throws we shall get 
rather more tails than heads. There is a slight 
bias in the tails direction. 

Now at last we come to the point. The deter- 
mination of sex depends on chance, with a bias 
towards the male sex. The questions are: What 
are all the factors which influence the chance ? 
Can we direct them ? And what causes the bias ? 

The Determination of Sex 

The sexual cells produced by men are called 
spermatozoa, or better, sperms. I spend most of 
my time studying sperms, because I am interested 
in birth control, and I want to invent ways of 
preventing them from fertilizing eggs. Sperms 
are microscopic little things looking rather like 
tadpoles. Of course one can only see them under 
the microscope. It is fascinating to watch hundreds 
or thousands of them all swimming aimlessly but 
rapidly in the field of the microscope, and still 
more fascinating to get just one in the field of 
view of the highest power lens and consider that 
in that microscopic speck there lies the whole 
inheritance from the father, the factors that 
would affect the development of every part of the 
offspring if it were allowed to fertilize an egg. 

The eggs produced by women and nearly all 
mammals are minute, but not so small as the 
sperms. They contain the inheritance from the 
mother. The first sperm to reach the egg fuses 
with it, and the single cell formed by their fusion 
grows into the embryo. Directly the sperm has 
fused with the egg, changes take place in the egg, 
which make it impossible for the other sperms to 
fuse with it. All the other sperms die. 

There are two sorts of sperms, male-producing 
and female-producing. That is not a theory: it is 
a fact. It is a fact which is totally ignored by the 


Biology in Everyday Life 

ignorant people who pretend that they know how 
to control sex. The female-producing one has got 
a rod-shaped body in it called an X chromosome. 
You can see it in the developing sperm. The male- 
producing sperm has no X chromosome. If you 
are a woman, you have got an X chromosome 
derived from your father in every cell in your 
body. If you are a man, you have not got a single 
X chromosome derived from your father in your 
body. The X chromosome derived from the 
father makes the embryo grow in the female 
way. In its absence the embryo grows in the male 
way. It all depends on which sort of sperm 
happened to fertilize the egg from which you 
grew. And what decided that ? Mainly chance. 

About five million sperms compete for one 
egg. They all swim about at random until one 
reaches it. If you let a mixed flock of a hundred 
black sheep and a hundred white sheep loose in 
a field and left the gate open, the chances would 
be equal whether a white sheep or a black sheep 
would wander out first. But if white sheep hap- 
pened on the average to be a little more active 
than black sheep, the chances would be slightly 
in favour of a white sheep getting out first. Make 
the assumption that the white sheep are on the 
average a little more active. Then, if you tried the 
experiment repeatedly, perhaps a black sheep 


The Determination of Sex 

would get out first in 100 cases and a white sheep 
in 1 10 cases. 

That seems to be analogous to what happens 
with sperms. We know for certain that male- 
producing sperms are produced in exactly the 
same number as female-producing sperms, yet 
more boys are conceived than girls. We do not 
yet know what the advantage is that male-produc- 
ing sperms have. 

You have to imagine the sperms all swimming 
about in a tube inside the body of the woman. 
They start at one end; the egg is up at the other 
end. They do not swim in any particular direc- 
tion. Someone has shown that if you artificially 
put the sperms in at the wrong end, near the eggs, 
some of them find their way down to where they 
ought to have started; and they find their way 
down just as fast as they ordinarily find their way 
up. What factors decide which sperm shall be 
the one that gets to the egg first? It depends on 
where each sperm happens to be at the start; 
what direction it happens to be pointing in ; how 
thick the fluid is through which it happens to 
have to swim at each part of its course ; how many 
times it happens to bump into another sperm and 
into the wall of the tube; in what direction its 
course is deflected when it does so ; what currents 
it meets in the fluid in which it swims; exactly 


Biology in Everyday Life 

where the egg happens to be placed in the tube; 
and so on. There are so many independent factors 
that it is nearly a case of pure chance, but not 
quite, because male-producing ones do have some 
slight advantage, and do get to the egg first 
rather more often than the female-producing 

You must notice that the egg has not the least 
tendency to grow into one sex rather than the 
other. It is absolutely indifferent. That again is 
not a theory: it is a fact. It applies to man and all 
hairy animals, but funnily enough in birds things 
are the other way round. In birds every egg is 
determined as either a male-producer or a female- 
producer. In birds there are not two sorts of 
sperms: they are all the same. But in mankind 
and in all other mammals that have been studied, 
the egg has nothing to do with sex determination. 
The sperm decides it. 

One odd guess that turns up from time to time 
is that one ovary produces male-producing eggs 
and the other one female-producing eggs. It is 
possible to say quite definitely that that is not so. 
You can completely remove one ovary, but the 
sex of the young ones produced is still mixed. 
The egg has nothing whatever to do with the 
matter in mammals. 

Another guess is that the time of conception 


The Determination of Sex 

makes a difference. That is an old midwives' tale. 
The whole question has been most carefully 
analysed, and it has been shown that in man the 
time of conception does not influence the sex 
ratio. In cattle the matter has been investigated 
on a huge scale, and it has been proved statistically 
that the time of service does not make the least 
difference to the proportion of the sexes. 

How can these erroneous ideas have gained 
ground ? That is not difficult to answer. Someone 
gets a "hunch" about the matter. Perhaps it is 
someone who has had several boys running. So 
she tells a lot of people how she thinks she has 
managed it, and they do likewise. Possibly a 
book is written about it. Some of the people who 
hear about it have a boy straight off, or two boys, 
or even three boys, and they think it is a case of 
cause and effect. They write and tell her, and she 
is confirmed in her opinion. The people who do 
not get what they want do not generally bother 
to write. You see, we expect on pure chance that 
a certain proportion of couples will have three 
boys running. You remember that we discussed 
all that when we were talking of tossing coins. 
One can calculate mathematically what propor- 
tion of families of three may be expected to 
consist of three boys, when the sex ratio at birth 
of the whole population is 105 boys to 100 girls. 


Biology in Everyday Life 

The calculated proportion of all-boy families is 
what you would expect on the assumption of 
chance coupled with the slight bias in favour of 
the male-producing sperm that we have spoken of 

If you happen to have six girls and no boys, 
you are very likely to think that there is some- 
thing peculiar about you that makes you especially 
prone to have girls. It is not so. It is exactly 
analogous to getting six heads running when you 
toss coins. It happens with coins approximately 
as often as it happens with babies. If you have 
six girls, the chances are still about even what 
the sex of your next child will be. Of course, it 
may be a girl again. On pure chance we should 
expect a minute number of families of a dozen 
girls and no boys, if people had families as big as 
that nowadays. The unfortunate parents would be 
unable to imagine it as a case of chance, but it is 
chance all the same. 

I can say quite definitely and certainly that 
there is at the moment no known method by which 
people can influence the sex of the children they 
conceive. I repeat that there are all sorts of 
superstitions that one can follow, and pure 
chance will give the desired result to a certain 
calculable proportion of the people who follow 
the superstition. The people who get the desired 


The Determination of Sex 

effect will naturally make the mistake of imagining 
that it is a case of cause and effect. 

Now suppose I said this: "Wear a brass ring 
round your little finger, and you will have only 
boys." If I said it sufficiently forcibly, probably 
lots of people would go off and do it. The next 
child would be a boy in about half the cases 
rather more than half really, because of the bias 
in favour of the male-producing sperms. The ones 
who got boys would be very much pleased and 
would think me very clever. Roughly half of the 
lucky ones would have a boy again at the next 
birth, and roughly half of these would go ahead 
and have a third boy, unless they stopped having 
children. Well, these extra lucky ones would 
probably think me a perfect genius, but actually, 
of course, chance would have brought about the 
result, not the brass ring. 

Shall we ever be able to control the sex of our 
children ? Of course, I cannot say. I can only give 
my opinion, to which I am as much entitled as 
the gentleman with the unusual headgear. My 
opinion is that it is very probable that we shall. 
Someone has got to think out a way of separating 
male-producing from female-producing sperms: 
that is all. It sounds easy, and it is a thrilling 
problem that has attracted a lot of people, but no 
one has solved it yet. 


Biology in Everyday Life 

If the female-producing sperms were larger 
than the male-producing (and there is some evi- 
dence they are), we might one day be able to 
make some sort of a filter to separate them. I 
have got a large glass tube in my laboratory 
reaching from the floor to the ceiling. I fill it with 
fluid and put sperms in at the top and wait. Their 
weight causes them gradually to sink to the 
bottom. I hoped that the female-producing sperms 
would sink more quickly than the others, but 
nothing came of it. Professor Huxley and I also 
tried racing them along horizontal tubes. We 
made them all swim towards the same direction 
by sending a weak electric current through the 
fluid in the tube. Sperms tend to swim towards 
the positive pole. We fondly imagined that they 
might conveniently sort themselves out into two 
groups. The group that got to the pole first would 
be the male-producing ones, we thought. But 
they did not sort themselves out at all. On the 
contrary, they remained in a single group. So that 
was no good. 

You see, we know how sex is determined by 
the sort of sperm that chances to reach the egg 
first. But we cannot control it yet. We cannot give 
one sort of sperm an advantage over the other. It 
is tantalizing to think of two and a half million 
male-producing sperms and two and a half million 


The Determination of Sex 

female-producing sperms all swimming about at 
random, and the decision being left almost to 
chance. It is tantalizing because many people are 
desperately anxious to have a child of a certain 
sex, and there are millions of the right sort of 
sperms there, but we cannot control them. If only 
we could find out the nature of the advantage the 
male-producing sperms have, we might be able 
to give them an even greater advantage artificially. 
But that is one of the many unsolved problems 
of biology. 

Only a few months before the publication of 
this book two workers in Moscow published a 
preliminary note on a method by which they 
claim to be able to separate the two sorts of 
sperms. They use an electric current, but in quite 
a different way from Professor Huxley and me. 
I remain sceptical until much larger figures are 
available. The results as they stand might be due 
to chance. Whether this will really be found to be 
a dependable way of separating the two sorts of 
sperms or not, I do not know, but I do think it 
very probable that one day we shall be able to 
separate them. Then what ? 

People have often said to me that if we could 
decide the sex of our children, nearly everyone 
would have boys, and the race would almost die 
out. Certainly there would be a chance of every- 


Biology in Everyday Life 

thing being topsy-turvy at first, and for a year or 
two we might get some extraordinary sex ratios. 
But I don't think it would go on. When Mrs. 
Jones and Mrs. Smith and Mrs. Williams and 
Mrs. Robinson had all had a succession of boys, 
just think what excitement there would be when 
Mrs. Johnson went and produced a girl! Girls 
would have quite a rarity value. Also I have found 
that people in genera] do not really want to have 
boys only. Most people prefer a mixed family. 
I consider myself lucky because I have got a 
girl and a boy. You must not think that I arranged 
it. It was chance, as in the case of every human 
family that has ever been conceived. 

The people who would benefit chiefly from the 
power to control the determination of sex would 
be people who by chance have had several children 
of one sex and none of the other. The nation as a 
whole might benefit also, because it is generally 
best to have about the same number of men as 
women in any non-polygamous country. Although 
more boys are born than girls, boys are more 
delicate on the average, and men tend to be killed 
in accidents more than women and also to die 
younger without accidents, so we always have 
more women than men, and many women can 
never marry. At every age above 1 9 there are more 
females than males. In 1921 there were 118 

The Determination of Sex 

women aged 20-24 to every 100 men, and 120 
women aged 2529 to 100 men of the same age, 
Here are the figures for each of the succeeding 
five-year groups: 119, 116, 113, 107, 107, 109, 
113, 119. The next group is the age-group 70-74. 
Look how the preponderance of women increases 
rapidly at these ages: 134, 148, 168, and finally 
at ages of 85 and more, 205 women to every 
100 men. 1 

The State could easily keep the sexes about equal 
if it wanted to, if we could control the sex ratio. 
It would not be difficult to think out some way 
of encouraging people to have children of the 
required sex. Control of things that previously 
were not controllable is one of the applications of 
science. Control of the sex ratio would be just 
one example of it. Pure science aims simply at a 
description of the universe, but one of the effects 
of science is to give us control over nature. We 
must think quickly, so as always to be prepared 
to use our control in the way that gives the greatest 
benefit to the greatest number. 2 

1 A. M. Carr-Saunders and D. Caradog Jones, The Social Structure 
of England and Wales, Oxford, 1927. 

* For a more detailed account of the determination of sex, see J. R. 
Baker, Sex in Man and Animals, Routledge, 1926. See also F. Okland, 
Is it a Boy?, Allen and Unwin, 1932. 


The Quality and Quantity of Mankind 

THERE is no evidence that our inborn nature, 
bodily or mental, has evolved since the beginning 
of civilization. There is no reason why it 
should have evolved. Evolution is supposed to 
happen in wild life because the ones that chance 
to be the fittest to survive are the ones that do 
survive. We know that vastly more young are 
born in every species than grow up and reproduce 
their kind. On the average it will be the ones that 
happen to be well equipped for the battle of life 
that will survive. The young ones may inherit 
the advantages that ensured their parents' 

In social animals this survival of the fittest does 
not act so much on the individual as on the herd. 
When a herd is attacked, the strong and brave 
members of it are more likely to be killed than 
the weaklings. An individual which would not be 
capable of finding its own food for itself might 
easily survive in herds. It would rely on the 
leaders to bring it to good pastures. Survival of 
the fittest would apply rather to the fittest herd 
than to the fittest individual. Weaklings could be 

The Quality and Quantity of Mankind 

tolerated until they seriously undermined the 
efficiency of the herd as a whole: then the herd 
would tend to get wiped out as a whole, from 
attacks of enemies or inability to find food. 

I think that if we remember this, we may find 
a clue to the meaning of polygamy. In many social 
animals the males have several wives. The sexes 
are about equal in numbers, so of course many 
males get no wives. That seems a bad arrange- 
ment, but is it really bad ? The males fight together 
for the possession of the females. You see that in 
many sorts of social animals deer, for instance, 
or seals. It is only the brave and strong ones that 
can mate and have young. The weaklings in the 
herd are tolerated, but in the polygamous species 
they do not have any young, and so they do not 
transmit their weakness to offspring. I think that 
that must be partly why polygamy is much 
commoner in animals that live in herds than in 
animals that do not. But there are exceptions to 
everything in biology, and the wild-duck is 
strictly monogamous when living a wild life, 
although it is a social animal, and the lion is 
sometimes polygamous, although it does not live 
in herds. We must take full account of these 
exceptions, but nevertheless we can see that social 
janimals would gain a certain advantage from 
'polygamy. It would help them to avoid the one 

E 6 S 

Biology in Everyday Life 

great disadvantage of social life to the species, 
the preservation of the unfit. 

What is the primitive condition of mankind 
as regards marriage ? Was he polygamous, or did 
he stick to one wife in prehistoric times, when he 
was just emerging from his ape-like ancestry? I 
do not know and nobody else knows, but there 
are many anthropologists who think there was 
what is called "group marriage", the mating of 
several people of one sex with several of the other. 
There is a good deal of evidence for it, mostly 
derived from a study of primitive people living 
in various parts of the world to-day. It is largely 
based on their having no special word for 
"mother". They call their mothers by the same 
name as they call all the other women whom 
their fathers would have been allowed to marry. 
And it is the same with their fathers: they have 
no special word for them. The evidence is most 
ingenious, but I doubt whether it is conclusive. 
I think I am right in saying that no animal 
practises group-marriage. Now polygamy is very 
widespread in social animals, and man is a social 
animal, and many races of man are to this cfay 
polygamous. It may be the natural condition. 

When reason replaces custom, the habits of 
mankind are changed ; and in the highest civiliza- 
tions monogamy has replaced polygamy, probably 


The Quality and Quantity of Mankind 

because of the trouble that is caused if there are 
a lot of unmarried men about. Civilized men do 
not want to be fighting all the time, and the 
natural tendency of polygamy is to make men 
want to fight for wives, and the ones who do not 
get any will be discontented. Also polygamy puts 
women into an undeserved position of inferiority, 
so that there are good reasons for encouraging 
monogamy. But there is one evil result. Since all 
males may marry and have children, the one great 
disadvantage of social life is encouraged: the 
weakling, who is preserved by the herd as a whole, 
may reproduce and transmit his undesirable 
qualities to his offspring; and the herd will take 
care of those too. 

It is instinctive in social animals to look 
after and protect feeble members of the herd. 
It is primarily an instinct to protect the young 
and the females, I suppose, but anyhow there 
must be this general altruistic defensive instinct 
in any herd, and it may extend to any member 
of the herd who is in difficulties. I used 
to have a cocker spaniel who had an extra- 
ordinarily strong instinct to protect my wife 
from strangers, and often he was very much 
worried if I played at all roughly with her. He 
thought she was being attacked, and he was on 
the defensive for her. 


Biology in Everyday Life 

Among ourselves we call this instinctive 
altruism "humanitarianism". It is quite neces- 
sary for our life as social animals. People differ 
extraordinarily in the amount of sex instinct and 
self-preservation instinct that they have got, and 
it is the same with the humanitarian instinct. 
Some people suffer nearly as much from seeing or 
thinking of other people suffering as from suffer- 
ing themselves. Other people seem scarcely 
affected by other people's sufferings. Obviously 
some sort of mean between the two is desirable. 
The anti-humanitarian the person who does not 
feel for others at all cannot help it any more 
than a man who is devoid of sex instinct: but he 
is quite unsuited to social life. The person at the 
other extreme lacks the amount of hardness that 
is often necessary for decisive, courageous action, 
and also he is not necessarily the person who 
actually does most to prevent suffering. 

This is the whole burden of what I want to say: 
normal people instinctively want to help the weak 
members of the community, but the result of this 
is that the weak members of the community 
survive and transmit their weakness to their 
children. So we are in a dilemma: what shall 
we do ? 

First of all, let us find out who are the weak. 
There are quite a lot of people who think that if 


The Quality and Quantity of Mankind 

only all the people who call themselves "upper- 
class" it really means just the rich people 
were to have lots and lots of children, and if only 
all the poor people were to have very few, we 
should be all right as a nation. Now that pre- 
supposes that the rich people are rich because 
they possess some inborn superiority over poor 
people. Well, do they? That is the first problem. 

So far as physical characters are concerned, 
there is a big average difference between rich 
and poor people. Rich people are on the average 
considerably taller (though, of course, there are 
plenty of tall poor people and short rich people). 
Someone measured the schoolboys aged 14 in 
Liverpool. 1 The average measurement at a second- 
ary school was 5 feet 2 inches ; at a council school 
in a poor district it was only 4 feet 7 inches. Pro- 
bably these physical differences between the 
classes are caused largely by differences in the 
food of the growing child. 

What about intelligence? That is a much 
harder problem. Is there any difference between 
the various classes in their inborn intelligence? 
How shall we find out? Obviously it would not 
be any good to test people in Latin to find out. 
The children of the professional classes usually 
learn Latin, and the children of labourers usually 

1 A. M. Carr-Saunders, Eugenics, Williams and Norgate, 1926. 

6 9 

Biology in Everyday Life 

do not, so we could not find out anything about 
intelligence in that way. Obviously our tests must 
not deal with subjects which are taught to one 
class and not to another. So far as possible they 
must not give an advantage to any special class. 
For instance, it would not be fair to ask, "How 
can one live on 155. q.d. a week?" because a rich 
person would not have the slightest idea, however 
intelligent he might be. 

The best tests are not perfect, but they do try 
so far as possible to avoid giving any benefit to 
people with special environments. There are tests 
for every age from 3 to 1 6. It has been found 
experimentally how hard each test must be for 
the average person of each age to be able to pass 
it, but not to be able to pass the test for the next 
higher age. The tests do not generally go farther 
than 1 6, because our intelligence does not seem 
to increase after 16. Of course, we go on getting 
more and more experience, but we do not get any 
more intelligent. I must admit, though, that some 
experience of life is quite essential to doing most 
of the tests. 

Here are a few examples from Terman's tests. 1 
Here is one for age 16. "Define the difference 
between character and reputation." I hope I 

1 R. Pintner, Imclligence Testing Methods and Results, University 
of London Press, 1924. 


The Quality and Quantity of Mankind 

agree with Mr. Terman on that. Here's one for 
age 12. "What similarities are there between 
wool, cotton and leather ?" Here is one for age 10. 
"Why should we judge a person more by his 
actions than his words?" One feels glad that one 
is not 10! Now age 3. "Repeat six or seven 
syllables, such as: 'I have a little dog'." Each test 
consists of a number of most varied questions. 

Idiots are people who never arrive at the 
mental age of 3. Imbeciles are grown-up people 
who pass the test for the mental age of 3 with 
flying colours, but fail at the test for 8. The 
Americans have a special word for people who 
can do tests for children of 8, but cannot do tests 
for children of 11. They call them "morons". 
The word "feeble-minded" is a general one for 
people whose intelligence fails to develop, so that 
their mental age is that of a child. 

A couple of investigators gave tests to 548 
children in American schools. They found the 
average marks obtained by the whole group. Then 
they grouped the children according to the class 
their parents belonged to professional, executive, 
artisan or labourer. They found that 85 per cent, 
of the children of the professional classes got 
more than the average marks; 68 per cent, of the 
children of the executive class got more than the 
average marks; only 41 per cent, of the artisans' 

Biology in Everyday Life 

children and 39 per cent, of the labourers' 
children got more than the average. A good many 
other people have made similar tests elsewhere. 
Someone found that 60 per cent, of the profes- 
sional class children got more than average marks. 
The figure for labourers' children was 47 per 

The general conclusion to be reached from a 
study of the results of these intelligence tests is 
this. High and low intelligences are distributed 
among every class of the community, but there is 
a tendency for people of high intelligence to be 
rather more abundant in the professional class 
than in the labouring class. Of course, the feeble- 
minded will usually tend to find their way into 
the poorest classes, and thus bring down the 
average of the intelligence of the poorest classes, 
however intelligent the people may be whose 
poorness is due to accident of birth. 

The general conclusion which I reach is that 
it does not matter very much, in the present 
circumstances, from what class of the community 
the next generation is chiefly derived, but the 
average innate intelligence would probably be 
somewhat higher if it were derived largely from 
the professional classes and somewhat lower if 
derived largely from the labourer class. But in 
any class we could find an abundance of people 

The Quality and Quantity of Mankind 

of the highest inborn intelligence who would be 
the most suitable parents of the next generation. 
Any class could provide such people, but there 
would be a somewhat higher proportion of them 
in the professional class than elsewhere. 

At the present time the professional classes 
have, on the average, considerably fewer children 
than the poorest people, and this is probably not 
in the best interests of the country. If the pro- 
fessional classes consisted simply of the people of 
the highest inborn intelligence, then it would be 
a tragedy for the nation for them to reproduce 
most slowly of all: but it is not so. It could only 
become so if everyone were given an equal chance 
of becoming a member of the professional class. 

It is possible for the children of very poor 
parents to get the best possible education, if they 
are lucky and intelligent and precocious, but it is 
difficult. Think how easy it is for the children of 
rich parents ! They can get a University education 
without any effort unless they are fools, and then 
they can pass on to a profession, Think what 
thousands of others are equally well equipped 
mentally, but have no possible chance of making 
the fullest use of their brains 1 What chance has 
the child of a poor man to become a doctor or a 
lawyer ? 

So long as we make it very difficult to pass from 


Biology in Everyday Life 

one class to another, it does not matter very much 
which class reproduces most rapidly. Now we 
must revert to a matter we have discussed before, 
the herd instinct. The normal herd instinct in 
animals acts for the benefit of the herd as a 
whole, but among men an extraordinary per- 
version of the herd instinct has arisen. People's 
sympathies tend to be for those other people who 
have about as much money as they have them- 
selves, and they transfer their herd instinct just 
to that group or class, and tend to be suspicious 
of other classes. People often pretend to a great 
patriotism, but (except perhaps in times of national 
emergency) the class feeling is a much more real 
thing than the unperverted instinct, which is a 
feeling of sympathy with other people of one's 
own race as a whole. It is this strong class feeling, 
which I regard as a perversion of the herd instinct, 
which prevents the best brains from getting 
surely to the top. 

If we really wanted above everything else that 
our race should flourish, we should give everyone 
a really equal chance to succeed, and should see 
to it that the people who had the highest inborn 
intelligence and energy were the ones who were 
actually doing the work requiring the most brains. 
Having found those people, we should encourage 
them to have as many children as would be con- 


The Quality and Quantity of Mankind 

sistent with the mothers' and children's health 
and welfare. The people who were inferior we 
would encourage to have few children. That 
would be true patriotism, something very different 
from the flag-waving and anti-foreign propaganda 
which now flourish under that name. 

I have mentioned that people of the professional 
classes have on the average considerably fewer 
children than poorer people. On the whole there 
is a tendency in England and many countries for 
people to have fewer children the richer they are. 
Why is this? It was not so a century ago. There 
seems to be little doubt that it is due to their 
using birth-control methods. It seems probable 
that the majority of couples among the rich and 
in the professional classes who are not sterile use 
some form of birth control. Poor people have less 
money to buy books about the subject, and in 
various ways their poverty disqualifies them from 
making use of the information. 

To understand problems of birth control it is 
essential to remember that our inborn instincts 
and natural fecundity are unlikely to have changed 
since the times of our ape-man ancestor. Evolu- 
tion probably only occurs as a result of the 
survival of the fit, not as a result of the survival 
of the offspring of those who have less sex instinct 
and less natural fecundity than their neighbours. 


Biology in Everyday Life 

We are therefore still adapted physiologically to 
the production of vastly more children than is 
now necessary. We have lowered our death-rate 
since those ancient times, and it is still falling. 
If we were to keep our birth-rate at the old figure, 
we should become seriously overpopulated. There 
is some likelihood that Great Britain is already 
overpopulated: I mean that we should have a 
higher average standard of living if we had fewer 
people. Economists generally fail to take sufficient 
interest in population problems. They would like 
to be clever enough to arrange a policy that would 
result in everyone having sufficient of the good 
things of life, whatever the population. As a 
biologist, I look at the matter differently. I should 
like to see our birth-rate controlled so as to give 
the highest possible average standard of living. 

Most people who use birth-control methods 
probably do so without any particular thought of 
the State as a whole. They are concerned with the 
health and happiness of the mothers and children 
concerned. A mother's life may be rendered 
almost intolerable by pregnancies following one 
another in quick succession, and there is evidence 
that children tend to be healthier when they are 
not born in quick succession. In poor families the 
birth of each child reduces the standard of living 
of the others. 


The Quality and Quantity of Mankind 

It is questionable whether very poor people, 
who cannot support large families, should be 
encouraged to have them. Every living man, 
woman and child has a right to work or full 
maintenance in any civilized state, and in the 
same way it may be argued that people have a 
duty to the State not to produce children which 
the State has to support, if the State is already 

Perhaps in the distant future we shall have a 
Ministry of Population. Its job will be to 
estimate the best population for the conditions, 
and to devise means of securing a decrease or 
increase of the birth-rate as required. If the 
politicians make the conditions different, the 
Ministry of Population will have to adjust the 

At the present moment there is no Ministry of 
Population, but the Ministry of Health allows 
Local Authorities to run birth-control clinics. 
Forty-one local authorities either have already 
established special clinics, or give birth-control 
information at gynaecological clinics, or refer 
cases to voluntary clinics or to private doctors, 
or authorize their medical officers to give advice. 
Nine others have decided to give birth-control 
advice, but have not started yet. Three others 
have lent premises to the National Birth Control 


Biology in Everyday Life 

Association for use as voluntary clinics. These 
figures come from the secretary of the Association. 
Voluntary clinics are run by this Association and 
also by the Constructive Birth Control Associa- 
tion and by the Society for the Provision of Birth 
Control Clinics. 

It is important to realize that in this country 
birth control is perfectly legal. It is legal to make, 
advertise, sell and use contraceptives. 

So far there has been little laboratory research 
on the subject, but things are moving forward. 
The Birth Control Investigation Committee is the 
body that organizes the laboratory research, and 
I am one of the workers under it. At present the 
birth-control methods are not absolutely reliable. 
No method can be countenanced that is harmful. 
The possibility of harmful effects is being investi- 
gated under the auspices of the Committee. The 
harmfulness of contraceptives has been made 
much of by people who could not tell a damaged 
tissue from a normal one, if provided with a 
perfectly good microscope and a perfectly good 
microscopical section of the tissue. Certain methods 
have been found to be quite harmless. 

We have seen that it probably does not matter 

tremendously what class of people reproduces 

most, so long as we go on making it difficult for 

people to rise from one class to another. But, 


The Quality and Quantity of Mankind 

apart from classes, is there any sort of person who 
ought not to reproduce ? 

To that I answer, " There certainly is." The 
congenitally feeble-minded person should not have 
children. If a normal person becomes feeble- 
minded as a result of a blow on the head, it does 
not matter if he or she reproduces, because the 
children will not inherit the defect; but if a 
person inherits feeble-mindedness, he or she will 
transmit it to descendants. We must distinguish 
between inherited and non-inherited feeble- 
mindedness. Goddard found that 54 per cent, 
of the feeble-minded people he studied had 
feeble-minded relations. Whole families of people 
have been studied in detail by Lidbetter, showing 
this feeble-mindedness in generation after genera- 
tion. There are notorious families in America in 
which feeble-mindedness has been passed on 
unceasingly. People sometimes argue that one 
cannot define the symptoms of inherited feeble- 
mindedness in such a way as to distinguish it 
from accidental feeble-mindedness, and there- 
fore there is no such thing as inherited feeble- 
mindedness. That seems to me a poor argument. 
It fails to take account of something that is 
common knowledge to biologists that a character 
may be affected in the same way by inheritance 
as by environment, 


Biology in Everyday Life 

The inheritance of congenital feeble-mindedness 
is not absolutely understood, but one form of it 
behaves like what is called a Mendelian recessive. 
That means that a person can suffer from it 
although neither of his parents did, and he can 
transmit it to his descendants, though not neces- 
sarily to his sons or daughters. Also it means that 
it is particularly likely to appear among the 
children of cousin marriages. If two feeble- 
minded people marry, all the children are likely 
to be feeble-minded. Sometimes all the children 
are not feeble-minded, and then people with a 
little knowledge of biology think that we really 
know nothing about the inheritance of it, because 
it does not fit in with simple Mendelian schemes. 
A little learning is a dangerous thing. It is not 
difficult to account for such cases, if one has an 
adequate knowledge of the laws of inheritance. 

There is a good deal of evidence that the 
feeble-minded are increasing in numbers in this 
country. They are careless of the consequences of 
their actions, and they reproduce rapidly. They 
appear to be a real danger to the State. They are 
the weak members of the herd. So now we are 
really back at what we were talking about at the 
beginning. The weak members of the herd in a 
polygamous species are protected and led to good 
pastures, but the weak males do not reproduce. 


The Quality and Quantity of Mankind 

Polygamy sees to that. We are not polygamous, 
so we must take other steps to prevent the repro- 
duction of the congenitally unfit. Men may be 
sterilized quite simply. This is a small and simple 
operation. A general anaesthetic is not required. 
A local one suffices. It is a fact that most people 
have not the slightest idea what the sterilizing 
operation is. They imagine it to be the same as 
castration, the operation carried out on male farm 
animals which are not required for breeding. It 
has nothing to do with that operation. That 
operation removes the sex instinct and changes 
the bodily growth of young animals. The steriliz- 
ing operation has no such effect. If a man were 
to be sterilized without being told what was being 
done to him, he would continue with his ordinary 
married life without the slightest idea that any- 
thing had happened to him. He would be sur- 
prised to find that he had no children. 

It should be made legal for any congenitally 
feeble-minded man to be sterilized if he agrees to 
it himself, if his wife agrees to it, and if the Board 
of Control gives consent. It is not proposed that 
anyone should be sterilized against his will, if he 
is sufficiently intelligent to express his will. 

For women the sterilizing operation is a major 
abdominal operation, and I am doubtful whether 
we should be justified in encouraging anyone to 

F 81 

Biology in Everyday Life 

undergo that except for reasons of personal 
health. What is wanted is some more research 
into simple ways of sterilizing women. The 
trouble with feeble-minded people is that they 
are too careless to use birth-control methods. 

Some people think that those who ask for the 
legalization of sterilization are anti-humanitarians, 
who want to attack the weakest members of the 
community. It is not so. The legalization of 
sterilization would be most humane, because it 
would prevent the birth of people who cannot 
hope to live really happy and useful lives. 

The newspapers are filled with politics, politics, 
politics: chiefly flag-waving and class war! Just 
occasionally a little paragraph is hidden away 
somewhere dealing with the really live issues 
that we have discussed in this chapter. We could 
cut out class war. We could make sure that talent 
always rose to the top. We could encourage the 
reproduction of the best stocks and prevent the 
reproduction of the unfit. We could make sure 
that the population of the country was adapted 
to its needs, and that mothers could always space 
births to the greatest advantage of their children 
and themselves. Any nation which decided on that 
course of action would rise supreme. 

Shall we continue just to muddle along anyhow? 
Probably we shall. 



War, Disease and Death 

"WAR is a biological necessity/' We have all 
heard that. At least, I confess I have not ever 
heard a biologist say it, but it is pretty generally 
accepted by lots of people, and it sounds learned. 
Let us examine it. What is at the back of people's 
minds ? 

I think it all comes from the struggle for 
existence and the survival of the fittest. We know, 
of course, that even the slowest breeding animals 
produce far more young than can ever grow up 
and themselves reproduce. There must be a con- 
tinual struggle to obtain a sufficiency of food and 
to avoid carnivorous enemies. Only the larger 
carnivores are free from any obvious attack. There 
is no animal that attacks them offensively, though, 
of course, the larger vegetarian animals will use 
all their strength in defending themselves against 
them. I say they are free from obvious attack, 
because of course they are not free from the 
attacks of parasites. 

Almost every animal one sees has its parasites. 
A favourite question in examinations for zoology 
students is the removal of the parasites from a 


Biology in Everyday Life 

frog. One need not bother to ask oneself whether 
the frogs one supplies to the candidates have got 
any parasites. They are all stuffed with them, in 
lungs, intestine and bladder. I have never come 
across an earthworm in which I could not find 
parasites. Wild mice are usually parasitized by 
fleas, and ticks are found on the skin of all sorts 
of beasts. Bats are often crawling with curious 
parasites. Birds have special insects living beneath 
their feathers. 

Obviously or not obviously, a great struggle 
for existence goes on in nature. Carnivorous and 
parasitic animals are utterly ruthless as to the 
suffering they cause (although, as we shall see 
later, it is generally not to the advantage of 
parasites actually to kill). 

The struggle goes on everywhere, but is it war ? 
What is war ? I think it is impossible to speak of 
war except in a social kind of animal. It is a fight 
between one herd and another herd of the same 
kind or a closely allied kind. 

Now let us review the whole animal kingdom 
and describe all the wars the different social 
animals have. Let us go right through all the 
different social mammals first of all, the ones I 
mentioned in the second chapter: the marmots, 
beavers, vizcachas, horses, deer, oxen, antelopes, 
sheep, goats, porpoises, dogs and wolves, seals, 

War, Disease and Death 

fruit-bats and social monkeys. Let us describe the 
different sort of war each kind goes in for how 
they fight herd against herd amongst the same 
kind the weapons and tactics they use, the 
biological significance of the whole thing. Shall 
we go right through that ? All right. 

It is a simple task, I am glad to say. War, as I 
have defined it, is simply non-existent in the 
animal kingdom, except possibly in the slave- 
making ants. Elsewhere, throughout the whole 
animal kingdom, 1 there is nothing remotely 
resembling war: and even in ants it is not really 
war according to our definition, because there are 
not fights between different nests of the same 
species or of closely allied species. So far is war 
from being a biological necessity that it is practi- 
cally biologically unknown except among human 

We must regard all races of man as being 
of the same kind or species, because a person 
of any race can marry one of any other race 
and have children who are themselves perfectly 
fertile, so far as is known. That is the only 
criterion of a single kind or species that we 
have that is of any value, though I admit it is 
not perfect. 

In social animals, each herd has its own 

1 One hive of bees sometimes attacks another. 


Biology in Everyday Life 

territory, and it never invades the territory of 
other herds. The territory instinct is extra- 
ordinarily strongly implanted in animals. 

Take the antelopes, just as a random example. 
The feeding-ground of each herd is sharply 
marked off. A herd never invades another herd's 
territory. Occasionally a few individuals may 
trespass across the boundary, but they are at once 
driven away, and they give the appearance of 
knowing that they are in the wrong, for they will 
not fight to maintain their position, as they would 
unhesitatingly if they were on their own ground. 
The dog is an example familiar to everyone. For 
the domestic dog his master's house and garden, 
if he has got one, represent the territory of the 
pack of his ancestors. A dog that never fights 
in the street (that is neutral territory) will fight 
ferociously if another dog happens to stroll in 
through the open gate. The dog that strolls in 
knows that he is in the wrong, and generally 
escapes as soon as possible, even if he is a bigger 
dog and ordinarily more ferocious. 

There is one antelope in particular that gives 
a splendid example of respect for the territory of 
others. 1 The springbuck of Bushmanland is a 
little yellow-coloured antelope similar to a gazelle, 
but differing in having a white stripe along the 

1 See Heape, quoted in footnote to p. 45. 

War, Disease and Death 

middle of the back over the haunches. Males are 
about thirty inches high at the shoulder. The 
springbuck lives in almost desert country. Like the 
lemming, it has periods of increased population 
during which starvation is threatened. At these 
periods, like the lemming, it emigrates. There are 
fertile areas all round except to the west, but they 
are occupied by another race of springbuck and 
by other kinds of antelopes. The springbuck of 
Bushmanland, although starving, does not go 
north or east or south. He could find plenty to 
eat there, but the ingrained instinct not to invade 
occupied territory is too much for him. He goes 
west in every sense of the term. He loses all his 
natural timidity and marches in enormous herds 
over country in which he cannot live towards the 
sea. If he comes to a village, he sweeps through 
it as though no longer afraid of man. The 
advancing army may be several miles wide and 
over forty miles long. It streams onwards, some- 
times crossing rivers. At last, after a march of 
about two hundred miles, it reaches the sea. All 
plunge in and are drowned. None return. To the 
springbuck this mad useless emigration is pre- 
ferable to an invasion of occupied territory. 

We reach this conclusion: herds of social 
animals have their own territories, and never start 
aggressive wars against other social animals of 


Biology in Everyday Life 

the same or closely allied species. If there is 
any individual trespassing, there is a strong 
defensive instinct which causes the trespasser 
to be ejected. 

I speak purely from the biological and not in 
the least from the military point of view when I 
say that to resist trespassing on one's own territory 
is probably instinctive and natural, while there is 
no biological basis for aggressive warfare. Mili- 
tarists sometimes think it necessary to carry out 
operations outside the home country in order to 
defend the home country, but in so doing they 
cannot rely on instinctive support from the people 
of their country; but when their country is 
actually invaded, then instinct probably prompts 

When we consider man's nearest allies among 
animals, we find that the male is commonly larger 
than the female, and the significance of this greater 
size is that he has an instinct to protect his wife 
and family. It would be useless to be bigger and 
stronger if there were no such instinct. The 
difference in size is not great in the orang-utan 
and chimpanzee, but it is very great in the gorilla. 
There is of course a considerable average dif- 
ference in size between the sexes in mankind, 
and one cannot fail to appreciate its significance. 
Men are almost certainly more innately ferocious 

War, Disease and Death 

than women. Women seldom really like having a 
good row with one another. However much they 
may like making what are called "catty" remarks 
in the absence of the person they dislike, they 
very seldom show their dislike openly to the 
person concerned. Now that is just what many 
men do like doing. I have often thought what a 
lucky thing it is that the differences between the 
sexes in mankind are so small compared with the 
differences one finds in many kinds of animals. 
Think what life would be like if men were as 
innately ferocious as bulls or male mandrills ! We 
are spared that, but it is nonsense to pretend 
that the two sexes are exactly equivalent as regards 
the instinct to fight when annoyed. 

I conclude that most men would find themselves 
almost driven by instinct to fight if their own 
territory were invaded by hostile foreigners, how- 
ever much opposed to war their reason might 
tell them to be. Even the Oxford Union would 
be less pacifist in the presence of an invading 

I have enormous sympathy with pacifists, but I 
think they tend to overlook men's innate instinct 
to protect their own territory. I am not saying 
whether it is a good instinct or a bad instinct: 
I am only saying that the instinct probably exists. 
When people try to overcome instincts, they 

Biology in Everyday Life 

generally have no success with the great majority 
of normal people. The medieval Church tried to 
overcome the sex instinct, and a few people still 
leave the world for monasteries and nunneries: 
but the race continues to exist. I often find that 
pacifists regard non-pacifists with something like 
horror. They would get a much more sympathetic 
hearing if they were more sympathetic themselves, 
and realized that the man who is prepared to fight 
for his own territory is probably only obeying his 
instincts in the same way as he does when he 
marries and has a family or refrains from walking 
about in woods alone at night. 

As for the aggressive militarist the man who 
wants his countrymen to fight abroad to increase 
his territory he cannot pretend that it is likely 
that there is any innate instinct to do that, as 
no animal does it, and we have no knowledge of 
any human instincts which do not occur also in 

That is enough about war. We have still two 
equally cheerful subjects ahead of us, disease and 

Obviously I am not going to look at disease 
in the ordinary way. You would have to get a 
medical man to do that. I want to look at disease 
from a biological point of view. We have seen 
that carnivores and parasites are absolutely ruth- 


War, Disease and Death 

less : it is all part of the never-ending struggle for 
existence. It does not matter to a parasite whether 
it makes the animal it lives on ill or not: its own 
survival is all that matters to it. Parasitic life has 
its obvious advantages: the parasite has not got 
to go searching for food. A flea can eat whenever 
it wants to. Nevertheless parasites are up against 
one big difficulty. It does not matter to them 
how much illness or pain they cause : but if they 
kill the animal they live on, then there is trouble. 
It usually means the death of them also. 

Suppose a man has got malaria. That means 
he has got some little single-celled animals inside 
his red blood-corpuscles. So long as he goes on 
living, these malaria germs are all right. Every 
now and then he may be bitten by a malaria 
mosquito. The mosquito sucks up some of the 
germs and infects somebody else with them later 
on. That is all right for the malaria germs. But 
suppose the malaria germs go and kill the man. 
What advantage do they get out of that? None 
at all. On the contrary, the result is that they all 
die themselves. That is why the vast majority of 
parasites do not kill the animals they live on: 
it would be death to themselves. In the course of 
evolution they will become better and better 
adapted to the animals they live on. They will 
avoid the most vital organs, and will not produce 

9 1 

Biology in Everyday Life 

any deadly waste products. It is generally only 
the maladjusted parasites that kill, the ones that 
have not yet become adapted to their hosts nor 
their hosts to them. Also death of both often 
occurs if a parasite happens to get into the wrong 
animal, because then neither is adapted to the 
other. In continental countries men are to some 
extent adapted to the influenza germ, and influenza 
is not usually a very serious illness ; but influenza 
is not a disease that occurs naturally in the western 
Pacific Islands, and the Melanesians are not 
adapted to it. The result is that if someone goes 
to those islands with influenza, the natives catch 
it and die off like flies. 

Sometimes it does not matter to a parasite if it 
kills its host in the end. There are animals called 
ichneumon flies that lay their eggs in or on the 
caterpillars of other insects. The eggs develop into 
caterpillars which live inside the other caterpillars 
and gradually eat them up. If they started eating 
the brain, their hosts would die, and they would 
die too as a result: so at first they only eat the 
less essential organs. Later on they do kill their 
hosts, but only when they are just ready to come 
out and change to the chrysalis stage. They do 
not eat in the chrysalis stage, so it does not 
matter that they have killed their hosts. 

There are just a few parasites that must kill 


War, Disease and Death 

their hosts for their own good. 1 These are 
microscopic animals that live in the muscles of 
fishes. They cannot get out through any of the 
apertures of the body, so they have only one way 
of getting from one fish to another, and that is 
by the death and disintegration of the one they 
are living in. They multiply enormously in the 
muscles, and the muscles are used up and the fish 
dies. Other fishes accidentally infect themselves 
when they come across disintegrated bits of the 
dead fish. Nothing of this sort happens with land 
animals. With them, death of the host usually 
means the death of all internal parasites. 

Thus it is not to the advantage of parasites to 
kill their hosts in the vast majority of cases. Never- 
theless they certainly do often kill them. A tre- 
mendous amount of human death does occur from 
diseases caused by parasites. What would happen 
if we prevented all disease caused by germs or 
parasties of every sort ? 

Suppose a very rich man in good health thought 
that the most worth-while thing in the world 
would be just to go on living. Well, he could get 
a special room made for himself, and have it 
sterilized so that it did not contain any germs. 
He could go through a course of treatment to 

1 E. A. Minchin, An Introduction to the Study of the Protozoa, Arnold, 


Biology in Everyday Life 

make sure he was free from all parasitic disease. 
Then one day he could have the surface of his 
body sterilized and with all the necessary pre- 
cautions he could enter his room. Only sterilized 
air would be allowed to enter the room. Nearly 
all his food would have to be cooked to prevent 
germs from getting in with it. Special precautions 
would have to be taken in introducing those 
vitamins that are destroyed by cooking. Double 
doors would have to be used for introducing any- 
thing into his room or removing anything from 
it; and when things were being introduced, it 
would be necessary to leave them for a bit between 
the double doors and meantime have the air 
between the doors sterilized. The man could only 
open his inner door when that had happened. 

With some such arrangement as this it would 
be possible for a man to make sure that he 
did not die of infectious disease. Would he live 
for ever, or is there such a thing as natural death ? 

In the young embryo, the cells that compose 
the body are not specialized for their various 
jobs. As the body grows up, they become special- 
ized in various ways, some as nerve cells in the 
brain, others as digestive cells in the intestine, 
and so on. As they become specialized, they lose 
their power of living. Irreversible changes tend to 
occur in them, which finally result in their death. 

War, Disease and Death 

Now this is the interesting thing: if you can 
change them back to their embryonic, unspecial- 
ized condition, you can give them a new lease 
of life. The length of time they have existed does 
not matter, if you can do that. 

With flat-worms you can do that. If you put 
some meat in an open bottle and leave the bottle 
in a pond for a few days, you will probable find 
some flat-worms in it. An ordinary sort is about 
an inch long when fully grown. In time it would 
die in the ordinary course of events, but if you 
put it in perfectly clean water and do not feed it, 
a very remarkable thing happens. 1 It uses up its 
own substance as food, and gets gradually smaller 
and smaller, until it is only a quarter of an inch 
long, and narrow in proportion. This is the 
interesting thing: the cells have become un- 
specialized, almost embryonic, the cells of a 
young animal. Of course, you could starve it to 
death : but if you now start feeding it, it grows 
and develops like a normal young flat-worm. 
You have given it a new lease of life. When it is 
full-grown, you can do the same thing again, 
and so on repeatedly. 

There is another way in which you can make 
cells become embryonic and so give them a new 

1 Child, Senescence and Rejuvenescence, University of Chicago Press, 


Biology in Everyday Life 

lease of life. If you cut the hinder four-fifths off 
a flat-worm, and keep just the head end, some of 
the cells of the head end become embryonic and 
start dividing and give rise to the whole of the 
missing part. When that has happened, you can 
do the same thing all over again, and again and 
again. It has been done thirteen times, and then 
the animals were only killed accidentally. One 
can certainly rejuvenate the cells of flat-worms. 

The trouble with the higher animals is that 
you cannot rejuvenate the nerve cells, the cells of 
the brain and spinal cord. When a nerve cell has 
once been fully formed in one of the higher 
animals, it never divides again. If it were to 
divide, there would be a chance, because cells 
commonly get a bit embryonic when they divide. 
In other tissues occasional cell divisions occur; 
but the cells in my brain are the self-same ones 
that will be there when I am an old man, except 
for those that have died off before I am old, and 
that is a thing that has probably started already, 
as I am thirty-two. So far, no one has thought 
of any way of rejuvenating old brain cells, or 
preventing them from gradually dying off. One 
can rejuvenate the rest of the body to some extent 
sometimes by giving gland extracts, or by stimu- 
lating certain ductless glands to do their work; 
but the brain goes on growing old. It is conceiv- 


War, Disease and Death 

able that one day someone might find a way of 
making nerve cells grow embryonic again. 

Natural death in man is probably death from 
old age of the nerve cells. Other parts of the 
body cannot go on long without the brain, 
though the skin does not die instantaneously at 
the moment of what we call death, and hair may 
continue growing for a bit after heart and lungs 
have ceased to act. 

Is natural death in the animal kingdom always 
the result of the death of nerve cells from old 
age? Certainly not. The Mayflies provide an 
obvious example. 

The nymphs of Mayflies live for one to three 
years under water in ponds and streams. One 
day, often in May, they come out of the water, 
cast their skin twice in rapid succession, and 
emerge as finished Mayflies. The finished Mayfly 
has only rudimentary jaws, inherited from an 
ancestor which used to eat: but they are useless. 
It has a mouth, but it is not used for eating. It 
has a digestive tube, but it is not used for digest- 
ing. It fills its stomach with air and can take in 
more or let part of it out. This process seems 
to have something to do in an obscure way with 
balancing, but it is difficult to see exactly how it 
works. Anyhow, it does not eat. It mates, lays 
its eggs if it is a female, and dies of simple 

c 97 

Biology in Everyday Life 

starvation of all its tissues. That is natural death 
for a Mayfly. Sometimes its natural life in the 
adult form is less than a day. 

Every law in biology has its exceptions, and 
the salmon seems to provide exceptions at every 
stage in its career, so I do not pretend to be able 
to lay down the law. I shall try to present the 
life-history of an average salmon very shortly, to 
illustrate this talk about death. There are dif- 
ferences of possible behaviour at almost every 
stage. 1 

Suppose some eggs were laid in gravel in 
shallow water in a river last November (1932). 
They will have hatched into tiny fishes, what are 
called "fry'* by now (spring), and by autumn 
they will be two or three inches long and they 
will have dark bands and spots on them. These 
"parr'* will live this winter and next winter in 
the river, but in the spring of 1934 they will 
lose their markings and become silvery, and their 
tail fins will become more pointed and they 
will migrate as "smolts" to the sea during the 
early summer. They will then live an entirely 
marine life for a bit. The following summer 
(1935) they may return to the river as "grilse", 
but others will wait until the summer of 1936, 

* P. D. Malloch, Life-History and Habits of the Salmon . . ." Black, 

War, Disease and Death 

or till the winter ; but perhaps still more of them 
will remain in the sea till the spring of 1937. 
Then they will come up from the sea to the rivers 
to breed, and when they come to a waterfall they 
will jump it. They can jump up to as much as 
ten feet at a time. Now the whole point is that 
from the moment they leave the sea they cease 
to feed. Meanwhile their reproductive organs are 
growing at the expense of their muscles. In 
November or later the females lay their eggs and 
the males pour the milt over it. The spent fish 
are called "kelts", and thousands of them may 
float helplessly downstream with the current and 
die. It is usually said that they have died of 
starvation, because they have not fed in the 
river; but I think the cause of death must really 
be largely the sudden change in bodily functions 
when the spawn and milt are discharged. The 
body is already enfeebled by lack of nourishment, 
and now this shock to its system usually kills it, 
though some return to the sea and eventually 
breed again in the river. 

Thus, different animals have different natural 
deaths. To keep a salmon alive unnaturally long, 
we might try to prevent it from allowing its 
reproductive organs to grow. To keep a Mayfly 
alive, we should have to devise means of nourish- 
ing it. To prolong human life, we should have 


Biology in Everyday Life 

to find out how to make the nerve cells embryonic 
once more. We have seen, from our study of the 
flat-worm, that that is not theoretically impossible. 
Lastly, the llama. I should say the huanaco, 
because I mean the wild beast, not the tame 
variety. He is a sort of humpless camel, and he 
lives in the desolate stony plains of Patagonia 
in South America. He lives his life in herds, far 
from any cover or concealment. When he is 
going to die, a strange instinct comes over him. 
He makes for a special spot at the southern 
extremity of Patagonia. There, on the banks of 
a river, are thickets of small twisted trees. This 
lover of open plains squeezes himself in under 
the branches and deposits his bones with those 
of generations of his ancestors. Hudson 1 thinks 
it is an instinct inherited from the time when his 
ancestors were forest animals which always 
retreated to cover when in danger or difficulty. 
If so, it is a retained useless instinct like our own 
instinct of clinging on tightly with our hands and 
even with our toes when we are frightened, which 
is quite useless to us now that we no longer live 
in trees. 

1 See footnote to p. 39. 




Professor of Genetics, University of London 
Head of Genetical Department, John Innes Horticultural Institution 


Biology and Statesmanship 

I LIKE controversy, and I confess I had rather 
hoped that Dr. Baker would have given me an 
opportunity of smiting him hip and thigh. 
Unfortunately I agree with almost everything he 
has written. But not quite everything. This is 
largely because we have been engaged on different 
branches of biology. He knows a lot more than 
I do about animals; I know more than he does 
about human physiology and about statistics. 

Now how can the biologist help the statesman ? 
He cannot dictate a policy to him. However, he 
can tell him whether certain statements are true 
or not; and he can tell him what will be the 
consequences of certain actions. But the better 
biologist he is the more often he will say "I don't 
know". Above all, he can draw the statesman's 
attention to certain facts and say, "What are you 
going to do about them?", and he can make him 
look at old facts from a new angle. 

Let me give you an example of what I mean. 
What is a successful man? Some people mean a 
man who makes a lot of money; others would 
say a man who earns the esteem of his fellows, 


Biology in Everyday Life 

and is honoured by them. But the biologically 
successful man is the man who lives a long and 
healthy life, and leaves behind him a number of 
healthy children. Now in our society social 
success and biological success do not go together. 
The well-to-do classes in the towns live longer 
than the poor, but they do not have so many 
children; and even the richest groups in the 
towns do not live anything like so long as the 
poor agricultural labourers in the country. That 
simple fact shows that there is something pretty 
badly wrong with our society. The ambitious and 
intelligent men and women deliberately seek an 
environment which condemns them to premature 
death and sterility. Don't get away with the idea 
that our society is peculiar in this respect. In the 
Middle Ages the human qualities most admired 
were holiness and chivalry. They condemned 
their holy men and women to celibacy, and 
killed off their knights in war. Of course, sanctity 
and chivalry are not strongly inherited, but 
heredity probably counts for something in both, 
and we can see now that our ancestors did their 
best to breed out these qualities. In the same 
way we are breeding out the hereditary qualities 
which we admire. 

The same sort of thing is quite frequent in 
nature. Most of our British beetles can fly they 


Biology and Statesmanship 

do not fly a great deal, but it is worth their while 
to have wings to take them to suitable environ- 
ments from time to time. In the island of Madeira 
about a third of the beetles are wingless. It would 
seem that the advantages of flight are more than 
outweighed by the danger of being blown out to 
sea. In the same way there is reason to believe 
that in our society the feeble-minded are breed- 
ing quicker than the rest of the population. What 
ought we to do about it? A number of people 
consider that the feeble-minded, who are said to 
number three or four hundred thousand in 
England and Wales, should be sterilized and 
prevented from breeding. Sterilization is not, of 
course, castration, but in the case of men at least 
a trivial operation. Nevertheless it is an interesting 
fact that few, if any, of the biologists who have 
made important contributions to our knowledge 
of heredity have so far supported this programme. 
Let us see why not. In the first place feeble- 
mindedness is a very difficult thing to define, and 
is not strongly inherited. There are cases where I 
believe that sterilization would be justifiable. There 
is a peculiar and terrible form of cancer called 
glioma which attacks the eyes of children in the 
first year of their life. Unless one or both eyes 
are removed they invariably die, after great 
suffering, before the age of six. When patients 


Biology in Everyday Life 

who have been saved from death by removing 
their eyes have children, the majority of such 
children suffer like their parents. Here, I believe, 
is a case where sterilization would be justifiable. 
So it would in the case of certain other well- 
defined diseases affecting perhaps a few thousand 
people in the country. 

But feeble-mindedness is nothing so definite. 
The law defines feeble-minded persons as those 
who "require care, supervision, or control, for 
their own protection and that of others". I 
strongly suspect that I am feeble-minded myself 
according to this definition. I never can manage 
to pack all the things I need into a suitcase if 
I am going away. It may be my collar, my 
pyjamas, or my toothbrush that I forget, but 
fortunately I have a legally appointed guardian 
in the shape of my wife, who supervises my 
actions. At present anyone can be certified as a 
mental defective on the words of two doctors and 
a magistrate, and, since doctors and magistrates 
are human, they sometimes make mistakes. 

You cannot draw a sharp line, as you can in 
the case of some other inborn defects; nor was 
Dr. Baker quite correct in suggesting that 
feeble-mindedness is incurable. I could give 
examples to the contrary, but I would sooner 
tell you about my friend Professor X ? who is a 

1 06 

Biology and Statesmanship 

very distinguished Fellow of the Royal Society. 
Up to the age of ten he did not learn to talk, 
and would have been classified as an imbecile or 
an idiot. Then an aunt spent a year or so in 
teaching him to talk, and was quite successful. 
Or perhaps not quite. He still does not talk as 
clearly as he might. He will never get a job as a 
B.B.C. announcer. But he can design apparatus 
that will solve problems which no amount of 
talking would solve. I am glad to say that he 
has two fine children. 

Again, though feeble-mindedness runs in 
families, it is not strongly inherited. Dr. Baker 
quoted a statement of a certain Dr. Goddard on 
this subject. I feel sure that he has not read 
Dr. Goddard's books. Here is a quotation from 
one of them, about the parents of a feeble-minded 
child: "Both parents are feeble-minded. The 
father is very high grade, so that for a considerable 
time we were much in doubt as to how to classify 
him. His feeble-mindedness takes the form which 
makes him noted as being peculiar. He is ignorant, 
lives alone, but is a good workman, sober, honest 
and industrious. " A good workman, sober, honest, 
and industrious, but not good enough for Dr, 
Goddard. It seems to me perfectly monstrous that 
we should be asked to interfere with our fellows 
on evidence of this kind. There are no satisfactory 


Biology in Everyday Life 

statistics about the inheritance of mental defect. 
Those which exist seem 1 to show that if we could 
prevent all mental defectives from breeding it 
would take some centuries to halve the present 
proportion of them in our population. 

There is another grave objection to a policy of 
wholesale sterilization. It would certainly not be 
applied impartially as between different social 
classes. Let us see how such laws actually work. 
John Hill was a labourer with five children in 
the American State of Washington. As the 
children were half-starved, he stole a number of 
hams. He was sentenced to imprisonment for not 
less than six months or more than fifteen years, 
but the sentence was suspended during his good 
behaviour. The judge concluded that the family 
was mentally sub-normal, and suggested that 
he be sterilized, to which he consented. This may 
have been an excellent thing for the human race, 
but does anyone suggest that the same thing 
would have happened had Mr. Hill been the son 
of a millionaire ? 

The programme of the party now in power 
in Germany includes a number of so-called 
eugenic measures, intended to check the breed- 
ing of various types of defectives, and of 

1 I hope that further research may demonstrate that such 
measures would be more effective. 

Biology and Statesmanship 

persons who are not of "German race". As 
they describe people who do not share their 
political opinions as defective "minderwertig" is 
the word it would seem that a large proportion 
of the German people is regarded as biologically 
undesirable. In England self-styled eugenists have 
attacked poor relief, and transitional benefit for 
the unemployed, on the ground that this class is 
on the whole congenitally inferior. Now it seems 
to me that the danger of multiplication of the 
mentally defective is a real one; but there is a 
much more pressing and immediate danger. And 
that is that people of whom Governments do not 
approve should, on eugenic grounds, be sterilized, 
segregated or starved. To my mind the attempt 
to justify such measures on biological grounds is 
a prostitution of science, far more serious than 
the manufacture of high explosives, bombing 
aeroplanes or poisonous gases. We biologists 
cannot prevent statesmen from doing these things, 
but we can most emphatically protest against 
their being done in the name of biology, and 
in countries where speech is still free we 
can warn the public against this misuse of our 

The same sort of pseudo-scientific propaganda 
goes on about race. It may be that negroes are 
congenitally inferior to whites, or Italians to 


Biology in Everyday Life 

Swedes, but there is no scientific evidence for this. 
If you could suddenly exchange all the babies in 
a Kentish village and a South African kraal it is 
quite likely that the standard of civilization in the 
village would go down, and that in the kraal 
would go up. But I don't know; nor does anyone 
else. Studies of whites and negroes living side by 
side under like conditions on a West Indian 
island showed no great differences in intellectual 
endowment between the two. In most countries 
the negroes enjoy far worse social and educational 
advantages than the whites, and no fair com- 
parison can be made. If you want to see which of 
two cows gives most milk you put them both in 
the same field; you don't put one in an English 
meadow and the other on the African veldt. So 
with men and women. 

There is one more reason why a eugenic pro- 
paganda which seeks to check the breeding of 
certain classes is a little misleading. The popula- 
tion in this country is still rising, but fertility 
has fallen so greatly that it will soon begin to 
diminish. If you take a hundred new-born English 
girls and assume that fertility does not fall any 
farther (which it almost certainly will), you find 
that, on the average, they will only have about 
eighty daughters, twenty less than are needed 
to keep the population steady. Even if medicine 


Biology and Statesmanship 

were so perfected as to abolish all deaths under 
thirty, the population would still diminish. 

Now it may be that this country would be 
better off with a somewhat smaller population, 
but it is fairly clear that the immediate problem 
is rather to encourage the propagation of the 
desirable majority of the nation rather than to 
discourage that of the undesirable minority. The 
drop in fertility is not wholly, perhaps not mainly, 
due to birth control by contraceptives. It has 
occurred in Italy where contraceptives are effectu- 
ally forbidden by law, and in Bavarian villages 
where they are forbidden by religion, as well as 
in England. Too many of our supposedly advanced 
thinkers are still thinking in terms of twenty years 
ago, when fertility was very much higher. 

Now this does not mean that nothing should 
be done to deal with mental defect. The first 
thing needed is a proper study of it. Think of 
eye defects causing weak sight. Some are con- 
genital, some acquired; some can be remedied, 
some cannot. But because short-sight is hereditary 
in some families we do not suggest that short- 
sighted people should be sterilized. We realize 
that they should wear the right kind of spectacles. 
A proper study of mental defect would perhaps 
show that some kinds are incurable and strongly 
hereditary. If so, there would be a case for 


Biology in Everyday Life 

sterilization of sufferers from those particular 
kinds. But it is as unscientific to lump all sorts 
of feeble-mindedness together, and treat them 
alike, as it would be to lump together all kinds of 
weak sight. 

What more general eugenic measures could a 
statesman take ? Beyond question the most imme- 
diately important eugenic measure is to avoid 
another war. There may be ethically justifiable 
wars I personally think there are but there 
are assuredly no biologically justifiable wars. In a 
modern war the heathiest young men in each 
fighting nation are killed off. The unhealthy 
remain behind and beget the next generation. 
War is a far more serious evil from the eugenic 
point of view than the multiplication of mental 

Secondly, a eugenical statesman would take 
steps to raise the birth-rate among all classes 
except the mentally or physically defective. One 
main reason for the falling birth-rate is probably 
that children are felt as an economic burden. 
This is inevitable under our present economic 
system. An institution such as hereditary wealth 
is clearly unsound biologically. For the fewer 
children you have the more you can leave to 
each. Moreover, childlessness is rewarded by a 
rise in the social scale. A man with no children 


Biology and Statesmanship 

or one is likely to save money; a man with ten 
cannot do so. Apart from luck, there are two keys 
to economic success, namely ability and sterility. 
So long as this is so, ability will tend to marry 
sterility; and able people to have fewer children 
than simpletons. The only cure for this state of 
affairs is some form of endowment of motherhood. 
I welcome the coming fall in our population 
because it will probably force the Government 
to do something concrete for mothers of large 
families the most exploited and least politically 
vocal group in our whole population. 

There is a tendency among people who have 
thought superficially on biology to support our 
existing social inequalities by analogy with the 
Darwinian struggle for existence and survival of 
the fittest. This is a mistake due to the confusion 
between social and biological success. If able men 
who became rich usually had large families, and 
failures who drifted into the slums had small ones, 
then our economic system would be biologically 
sound. Actually the opposite is the case. The 
biologist must welcome economic measures which 
tend, either to equalize incomes as between 
different social classes, or to equalize the standard 
of living as between members of large and small 
families in the same social class. 

I have been dealing with eugenics because 
H 113 

Biology in Everyday Life 

Dr. Baker raised this issue, not because I think 
that it is the most immediately important applica- 
tion of biology to politics. No eugenic measures 
could have much effect for a generation. What 
about the forty million people who are here now ? 
If you are looking after animals the first thing 
you must think about is their food. A diet which 
will keep them alive is not good enough to keep 
them healthy. If you want a stock of rats to grow 
as well as possible you must feed them properly. 
But that is not enough. Even though they have 
the best possible diet from the moment of birth 
you will not get the best results unless their 
mothers have been well fed too. It takes two 
generations before you can wipe out the results 
of bad feeding. The same is probably true of man, 
though the evidence is not so complete. You must 
be very careful of putting down physical defects 
in a child to bad heredity unless both it and its 
mother have had an adequate diet. 

Do English people get as good a diet as a 
biologist would prescribe for them ? Let us take a 
family of a man, a wife and three children. Recent 
calculations 1 show that an adequate diet for them 
would cost about 1 is. per week in London. 
This diet does not include such luxuries as tea 
and jam, let alone beer, but it is fully adequate 

1 Week-end Review, April i, 1933. 

Biology and Statesmanship 

as regards essential dietary constituents. Now it 
is obvious enough that some million English 
families have not got a guinea a week to spend on 
food. I need not quote rates of wages or of unem- 
ployment benefit to prove this. If you get less 
food than this physiological standard, or the same 
gross amount, but with less of certain desirable 
constituents such as fruit, greens and liver, you 
will not die of it. But you will not grow as fully 
as you might, and you will be more liable to 
various infections. 

A biologically minded Government would re- 
gard proper feeding as an important branch of 
national defence, which it is. For we have had 
wars with the Dutch, French, Russians, Germans 
and other nations. But these have been matters of 
a few years. We are all of us always at war with 
disease. Even between 1914 and 1918 a great 
many more English people were killed by the 
germs of infectious diseases than by our human 

I expect some of you think I am misusing my 
position as a biologist to make propaganda against 
our present Government; so to prove that I am 
trying to be scientific, I am going to talk about 
some social reforms of which I happen to be in 
favour, but which cannot be supported on bio- 
logical grounds. I should like to see agricultural 

Biology in Everyday Life 

labourers' wages raised. But this would not make 
them any healthier. They live about as long as 
the farmers who employ them. From the merely 
animal standpoint they are pretty well off. The 
poor in our towns are not even as well off as well- 
cared-for animals. 

Again, I should personally like to see the school- 
leaving age raised. But as a biologist I must at 
once admit that by the time they reach the age 
of 14 a good many children seem to be pretty 
incapable of learning anything more. There are 
large innate inequalities of intelligence, but neither 
cleverness nor stupidity is confined to any one 
social group. An educational system designed 
by a biologist would recognize that inequality. 
If you have very bright and very dull children 
in the same class you are being unfair to both. 
You keep back the bright, and go too fast for the 
dull. A proper educational system would greatly 
increase the number of free places and scholarships 
now available. Even in London there are not 
enough; almost everywhere else far too few. And 
such a system would also recognize the fact that 
not only does the level of intelligence which is 
finally reached vary, but so does the rate of 
getting there. The child whose intelligence 
matures quickest does not always get farthest in 
the long run. Our existing scholarship system 

Biology and Statesmanship 

seems to be designed to pick out precocious 
children. The hollyhock grows in height ten or 
twenty times as fast as the oak, but it does not 
get so far in the long run. We need an educational 
system that will encourage human oaks as well 
as human hollyhocks. 

Let me put the same point of view rather 
differently. In any community there must be 
inequality. We need skilled and unskilled workers, 
and there must be a few men and women in 
positions of authority. If everyone were born 
equal, it would not much matter how the various 
posts in society were allotted. But we are not 
born equal, far from it. The best community is 
that which contains fewest square pegs in round 
holes, bricklayers who might have been musicians, 
company directors who, by their own abilities, 
would never have risen above the rank of clerk. 
If ability was strictly hereditary, a rigid class 
system would be biologically justified. But we 
all know that wise parents may have foolish sons, 
and conversely. So a system of hereditary classes 
is not only unjust but inefficient. The greater the 
equality of opportunity, the greater the likelihood 
that the right man or woman will be found for 
any given post. Our society to-day is so complicated 
that we simply cannot afford to let much of our 
best human material go to waste, as it does to-day. 


Biology in Everyday Life 

But equality of opportunity does not mean 
equality for those who seize the opportunity and 
those who miss it. The biologist would demand 
so much equalization of incomes that no child 
should be born of a half-starved mother, itself 
inadequately housed and fed, and denied opportu- 
nities because its father had been a failure. He 
would not demand equal pay for the worker and 
the slacker, the genius and the dunce. If our 
society were organized to employ the productive 
resources which science has given it, there would 
be enough goods available to secure a satisfactory 
minimum for all, and a reasonable degree of 
luxury for those who had succeeded on their own 
merits. Under such a social system we might 
perhaps begin to think of restricting the breeding 
of social failures. To do so under our present 
system would in many cases merely be to add one 
injustice to another. 

The biologist is not merely concerned with 
men, but with other animals and plants. Some 
of these are our friends, some our enemies. Five 
hundred years ago we still had large-scale enemies, 
even in England. The last English wolves were 
killed in the reign of Henry VII. Wolves and 
wolf-hunting impressed themselves on the people's 
mind, so that the wolf left its name in such places 
as Wolverhampton, Wolverton, and Wolvercote. 


Biology and Statesmanship 

We still have non-human enemies, but they are 
smaller. Some, like the louse and the bed-bug, 
we can see with the naked eye. Others, like the 
bacteria which cause diphtheria and tuberculosis, 
we can only see with a microscope. Still others, 
for example, the causes of measles and smallpox, 
we cannot see even with a microscope. Now these 
are our real enemies. The flea, which carries 
plague, and the louse, which conveys typhus 
fever, have killed far more men than ever were 
killed by wolves. But we have never organized 
against them as we have against wolves, because 
they have never struck the people's imagination 
as enemies of man. If they had, we might have 
towns called Louserhampton and Disinfecton. 

The biologist realizes that there is a war on 
a very real war of man against disease. Un- 
fortunately, except for the doctors, nurses, research 
workers, and sanitary workers, such as the muni- 
cipal dustmen and sewermen, we are mostly non- 
combatants in this war. We wait till we have been 
attacked by bacteria, and then call in the doctor. 
Let us try to imagine what the world would be 
like if we had biologically educated statesmen 
backed by a biologically educated public. Do not 
think that we should all go about in fear and 
trembling. I do not go about in mortal terror 
because there are bacteria about, any more than 


Biology in Everyday Life 

I did in India because there were tigers and 
cobras there. But we would no more tolerate lice 
than we do man-eating tigers. We should say 
that the proper place for lice was in the Zoo, and 
we should organize a campaign to make them as 
extinct in England as the wolf is to-day. It would 
mean a pretty thorough overhaul of our slums, 
and about time too! We should no more tolerate 
a house that harboured bed-bugs than a forest 
full of tigers. 

And the same with infectious diseases. When 
the virus of smallpox lands on our shores we hunt 
it down as we should hunt down a foreign invader 
or a lion. But we do not take the same measures 
about measles. There are three reasons for this, 
We have not woken up to the fact that measles 
kills a great many more people than smallpox or 
tigers. The effort needed would be very con- 
siderable. And above all the effort would have to 
be international. It would be little use abolishing 
measles in England if nothing were done about it 
in France. But just imagine what an international 
war on disease and parasites would be like. Sup- 
pose the peoples and Governments of our own 
country and the Dominions, Europe, the United 
States and Japan, agreed to make a real effort to 
abolish the principal infectious diseases and 
parasites. We should have to clean ourselves up 


Biology and Statesmanship 

and impose a medical inspection and three 
weeks' quarantine on visitors from outside. We 
should have our setbacks. A case of diphtheria in 
Liverpool, and we should rush over armies of 
experts from the Continent to examine all possible 
contacts, and throw a ring round the area of 
infection. An outbreak of measles in Marseilles, 
and doctors from England and Germany would 
be flying south to help the French in their fight. 

You can say that this is a Utopian idea. But the 
spirit is there already in international medical and 
scientific congresses. They cut across the bound- 
aries of international hatred. The last two inter- 
national physiological congresses were in Boston 
and Rome. The next is to be in Moscow. There 
is international rivalry at such congresses; but it 
is a friendly rivalry. The English try to show 
the Germans that we have something new to tell 
them about the nervous system; the Germans 
show us what they have discovered about diges- 
tion. There are no secrets. We are all working 
for the same ends. And why? Because a discovery 
in medical science can only be used for the com- 
mon good. A sick foreigner is of no advantage 
to this country on the contrary, he is a possible 
source of infection. The more we realize the 
existence of these common enemies of all man- 
kind, the more we shall forget the enmities 


Biology in Everyday Life 

between men. That is why the inclusion of 
biology in our education and our common think- 
ing is one of the most powerful weapons that 
exist against international hatred. 

Some of you think that I should like to hand 
the world over to an international tyranny of 
doctors. But wait a bit. Is your doctor really a 
tyrant? Remember that the world to-day is 
largely run by business men, that is to say, men 
who work with a view to getting rich. They may, 
or may not, enrich others in the process. But 
the doctors cannot try to corner health. They 
have a very low death-rate from chronic ailments 
like cancer and heart disease, which can be tackled 
in their early stages ; but they die in large numbers 
of acute infections caught from their patients. The 
pursuit of wealth is generally competitive; that 
of health must be co-operative. My wealth is not 
your wealth, but my health is your health, because 
if I fall ill you are likely to contract the same 

You see then that biology can do two things 
for statesmanship. It can urge the statesman to 
certain definite reforms. But, still more important, 
it can deflect his mind from issues where one 
man's good is another man's harm, issues of 
military and economic rivalry, to issues of health 
where the interests of different classes and dif- 


Biology and Statesmanship 

ferent nations are one. There are higher points 
of view than the biological. Man is not merely an 
animal; but he is an animal, and in our political 
and economic thought we are apt to treat him as 
a machine for making commodities or a unit in 
an army. We may desire to educate him or to 
save his soul; but we differ very sharply about 
education and salvation. We are all agreed about 
the difference between a live and a dead man, and 
mostly about the difference between sickness and 
health. And the carrying out of biologically 
desirable reforms would be a wholetime job which 
would keep statesmen busy for a century. During 
that century they would have learned to treat their 
fellow-men not as rivals, but as colleagues. The 
human race would have become civilized.